-
MOBILE SIGNAL JAMMER USING ARDUINO
B.Tech. Project Report
A. Raja Gopal MD. Imthiyaz Ur Rahmaan
P. Nischal Reddy Y. Siva Sai Krishna Kumar Reddy
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY
(Affiliated to Jawaharlal Nehru Technological University)
HYDERABAD 500 090
2013
-
MOBILE SIGNAL JAMMER USING ARDUINO
Project Report Submitted in Partial Fulfillment of the
Requirements for the Degree of
Bachelor of Technology in
Electronics and Communication Engineering by
A.Raja Gopal (09241A0458)
MD.Imthiyaz Ur Rahmaan (09241A0482)
P.Nischal Reddy (09241A0487)
Y.Siva Sai Krishna Kumar Reddy(09241A04A5)
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY
(Affiliated to Jawaharlal Nehru Technological University)
HYDERABAD 500 090
2013
-
Department of Electronics and Communication Engineering
Gokaraju Rangaraju Institute of Engineering and Technology
(Affiliated to Jawaharlal Nehru Technological University)
Hyderabad 500 090
2013
Certificate
This is to certify that this project report entitled Mobile S
igna l Jammer Using Ard u ino by A. Raja Gopal (Roll
No.09241A0458), M D. Imth iyaz Ur Rahm aan (Roll No.09241A0482) , P
.Nischal Redd y (Roll No.09241A0487) and Y.Siva Sai Krishna Kumar
Reddy(Roll No.09241A04A5), submitted in partial fulfillment of the
requirements for the degree of Bachelor of Technology in
Electronics and Communication Engineering of the Jawaharlal Nehru
Technological University, Hyderabad, during the academic year
2012-13, is a bonafide record of work carried out under our
guidance and supervision.
The results embodied in this report have not been submitted to
any other University or Institution for the award of any degree or
diploma.
(Guide) (External Examiner) (Head of Department) N.Madhu Sudhana
Rao Dr.Ravi Billa Assistant Professor
(i)
-
ACKNOWLEDGMENT
It is a pleasure to express thanks to Prof. N.Madhu Sudhana Rao
for the
encouragement and guidance throughout the course of this
project.
It is a pleasure to express thanks to
1.Prof. K.N.Balajikumar
2. Prof. V.H.Raju
3.Prof. A.Radhanand
A. Raja Gopal ___________________________ MD. Imthiyaz Ur
Rahmaan ___________________________
P. Nischal Reddy ___________________________ Y. Siva Sai Krishna
Kumar Reddy ___________________________
(ii)
-
ABSTRACT
Mobile jammer is used to prevent mobile phones from receiving or
transmitting signals with the base stations. Mobile jammer
effectively disable mobile phones within the defined regulated
zones without causing any interference to other communication means
Mobile jammer can be used in practically any location, but are used
in places where a phone call would be particularly disruptive like
Temples, Libraries, Hospitals etc. As with other radio jamming,
mobile jammer block mobile phone use by sending out radio waves
along the same frequencies that mobile phones use. This causes
enough interference with the communication between mobile phones
and communicating towers to render the phones unusable. Upon
activating mobile jammer, all mobile phones will indicate "NO
NETWORK. Incoming calls are blocked as if the mobile phone were
off. When the Mobile jammers are turned off, all mobile phones will
automatically re-establish communications and provide full service.
Mobile jammers effect can vary widely based on factors such as
proximity to towers, indoor and outdoor settings, presence of
buildings and landscape, even temperature and humidity play a
role.
(iii)
-
CONTENTS Chapter 1: Introduction 01
Chapter 2: Hardware Equipment 02
2.1 Arduino 02
2.1.1 Features of Arduino 02
2.1.2 Power Supply to Arduino 02
2.1.3 ATmega 328 Microcontroller 06
2.2 Real time Clock 10
2.2.1 DS 1307 IC 10
2.3 Liquid Crystal Display 17
2.4 Relay 20
2.5 Signal Isolator 23
Chapter3 : I2C Communication 40
3.1 Introduction 40
3.2 Design 40
3.3 Reference design 41
3.4 Timing Diagram 43
3.5 Limitations 43
3.6 IC (wire) library 43 Chapter 4: Block Diagram and working
48
Chapter 5: Flow chart 49
Chapter 6: Program code 51
Chapter 7 : Applications and Advantages 58
Chapter 8 : Conclusion 59
-
List of figures Pin diagram of Atmega328 08
Pin diagram of DS1307 10
Block diagram of DS1307 11
Data transfer of I2C bus 12
Data write-slave receive mode 16
Data read- slave receive mode 16
Liquid Crystal Display 20
Circuit symbol of relay 21
Relay operation and use of protection diodes 21
Block diagram of transistor driver circuit 22
Relay interfacing with microcontroller 23
Block diagram of mobile jammer 29 White noise generator output
spectrum 33
Block diagram of IF section 35
Pin diagram of MAXIM 2623 35
MAXIM 2623 pin connection 36
Circuit diagram of RF section 38
Block diagram of project 48
-
List of tables Features of Arduino board 02
Oscillator Circuit 11
Timekeeping registers 13
Pins Functions LCD 18
GSM Frequency Bands 28
-
1
Chapter 1
INTRODUCTION Communication jamming devices were first developed
and used by military.
Where tactical commanders use RF communications to exercise
control of their forces, an enemy has interest in those
communications. This interest comes from the fundamental area of
denying the successful transport of the information from the sender
to the receiver.
Nowadays the mobile jammer devices are becoming civilian
products rather than electronic warfare devices, since with the
increasing number of the mobile phone users the need to disable
mobile phones in specific places where the ringing of cell phone
would be disruptive has increased. These places include worship
places, university lecture rooms, libraries, concert halls, meeting
rooms, and other places where silence is appreciated.
Mobile jammer is used to prevent mobile phones from receiving or
transmitting signals with the base stations. Mobile jammer
effectively disable mobile phones within the defined regulated
zones without causing any interference to other communication means
Mobile jammer can be used in practically any location, but are used
in places where a phone call would be particularly disruptive like
Temples, Libraries, Hospitals etc. Mobile jammers were originally
developed for law enforcement and the military to interrupt
communications by criminals and terrorists to foil the use of
certain remotely detonated explosives. The civilian applications
were apparent with growing public resentment over usage of mobile
phones in public areas on the rise & reckless invasion of
privacy. Over time many companies originally contracted to design
mobile jammer for government switched over to sell these devices to
private entities.
As with other radio jamming, mobile jammer block mobile phone
use by sending out radio waves along the same frequencies that
mobile phones use. This causes enough interference with the
communication between mobile phones and communicating towers to
render the phones unusable. Upon activating mobile jammer, all
mobile phones will indicate "NO NETWORK. Incoming calls are blocked
as if the mobile phone were off. When the Mobile jammers are turned
off, all mobile phones will automatically re-establish
communications and provide full service. Mobile jammers effect can
vary widely based on factors such as proximity to towers, indoor
and outdoor settings, presence of buildings and landscape, even
temperature and humidity play a role.
The choice of mobile jammers are based on the required range
starting with the personal pocket mobile jammer that can be carried
along with you to ensure undisrupted meeting with your client or a
personal portable mobile jammer for your room or medium power
mobile jammer or high power mobile jammer for your organization to
very high power military jammers to jam a large campuses.
-
2
Chapter 2 Hardware equipment
2.1 Arduino
The Arduino Uno is a microcontroller board based on the
ATmega328. It has 14 digital input/output pins (of which 6 can be
used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator,
a USB connection, a power jack, an ICSP header, and a reset button.
It contains everything needed to support the microcontroller;
simply connect it to a computer with a USB cable or power it with a
AC-to-DC adapter or battery to get started.
2.1.1 Features of Arduino board
Microcontroller ATmega328
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limits) 6-20V
Digital I/O Pins 14 (of which 6 provide PWM output)
Analog Input Pins 6
DC Current per I/O Pin 40 Ma
DC Current for 3.3V Pin 50 mA
Flash Memory 32 KB (ATmega328) of which 0.5 KB used by boot
loader
SRAM 2 KB (ATmega328)
EEPROM 1 KB (ATmega328)
Clock Speed 16 MHz
2.1.2 Power To Arduino
The Arduino Uno can be powered via the USB connection or with an
external power supply. The power source is selected
automatically.
-
3
External (non-USB) power can come either from an AC-to-DC
adapter (wall-wart) or battery. The adapter can be connected by
plugging a 2.1mm center-positive plug into the board's power jack.
Leads from a battery can be inserted in the Ground and Vin pin
headers of the POWER connector.
The board can operate on an external supply of 6 to 20 volts. If
supplied with less than 7V, however, the 5V pin may supply less
than five volts and the board may be unstable. If using more than
12V, the voltage regulator may overheat and damage the board. The
recommended range is 7 to 12 volts.
The power pins are as follows:
VIN. The input voltage to the Arduino board when it's using an
external power source (as opposed to 5 volts from the USB
connection or other regulated power source). You can supply voltage
through this pin, or, if supplying voltage via the power jack,
access it through this pin.
5V.This pin outputs a regulated 5V from the regulator on the
board. The board can be supplied with power either from the DC
power jack (7 - 12V), the USB connector (5V), or the VIN pin of the
board (7-12V).
3V3. A 3.3 volt supply generated by the on-board regulator.
Maximum current draw is 50 mA.
GND. Ground pins.
Each of the 14 digital pins (pins 0 to 13) on the Uno can be
used as an input or output, using pinMode(), digitalWrite(), and
digitalRead() functions. They operate at 5 volts. Each pin can
provide or receive a maximum of 40 mA and has an internal pull-up
resistor (disconnected by default) of 20-50 k. In addition, some
pins have specialized functions:
Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit
(TX) TTL serial data. These pins are connected to the corresponding
pins of the ATmega8U2 USB-to-TTL Serial chip.
External Interrupts: 2 and 3. These pins can be configured to
trigger an interrupt on a low value, a rising or falling edge, or a
change in value.
PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the
analogWrite() function.
SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support
SPI communication using the SPI library.
LED: 13. There is a built-in LED connected to digital pin 13.
When the pin is HIGH value, the LED is on, when the pin is LOW,
it's off.
The Uno has 6 analog inputs, labeled A0 through A5, each of
which provide 10 bits of resolution (i.e. 1024 different values).
By default they measure from ground to 5 volts, though is it
possible to change the upper end of their range using the AREF pin
and the analogReference() function.
-
4
The programs written for Arduino are called sketches. For the
sketch to work on your Arduino Uno, there are two hardware related
settings you need to make in the Arduino IDE
Board Serial Port
The basic structure of the Arduino sketch is fairly simple and
has two required functions: void setup() { statements; } void
loop() { statements; } Where setup() is the preparation, loop() is
the execution. Both functions are required for the program to work.
The setup function should follow the declaration of any variables
at the very beginning of the program. It is the first function to
run in the program, is run only once, and is used to set pinMode or
initialize serial communication. The loop function follows next and
includes the code to be executed continuously reading inputs,
triggering outputs, etc. This function is the core of all Arduino
programs and does the bulk of the work.
setup() The setup() function is called once when your program
starts. Use it to initialize pin modes, or begin serial. It must be
included in a program even if there are no statements to run. void
setup() { pinMode(pin, OUTPUT); // sets the 'pin' as output }
loop() After calling the setup() function, the loop() function
does precisely what its name suggests, and loops consecutively,
allowing the program to change, respond, and control the Arduino
board. void loop() { digitalWrite(pin, HIGH); // turns 'pin' on
delay(1000); // pauses for one second digitalWrite(pin, LOW); //
turns 'pin' off delay(1000); // pauses for one second }
-
5
pinMode(pin, mode) Used in void setup() to configure a specified
pin to behave either as an INPUT or an OUTPUT. pinMode(pin,
OUTPUT); // sets pin to output There are also convenient pullup
resistors built into the Atmega chip that can be accessed from
software. These built-in pullup resistors are accessed in the
following manner: pinMode(pin, INPUT); // set pin to input
digitalWrite(pin, HIGH); // turn on pullup resistors Pull-up
resistors would normally be used for connecting inputs like
switches. Notice in the above example it does not convert pin to an
output, it is merely a method for activating the internal pull-ups.
Pins configured as OUTPUT can provide 40 mA (milliamps) of current
to other devices/circuits. This is enough current to brightly light
up an LED (don't forget the series resistor), but not enough
current to run most relays, solenoids, or motors. Short circuits on
Arduino pins and excessive current can damage or destroy the output
pin, or damage the entire AT mega chip. It is often a good idea to
connect an OUTPUT pin to an external device in series with a 470 or
1K resistor.
digitalRead(pin) Reads the value from a specified digital pin
with the result either HIGH or LOW. The pin can be specified as
either a variable or constant (0-13). value = digitalRead(Pin); //
sets 'value' equal to // the input pin
digitalWrite(pin, value) Outputs either logic level HIGH or LOW
at (turns on or off) a specified digital pin. The pin can be
specified as either a variable or constant (0-13).
digitalWrite(pin, HIGH); // sets 'pin' to high
analogRead(pin) Reads the value from a specified analog pin with
a 10-bit resolution. This function only works on the analog in pins
(0-5). The resulting integer values range from 0 to 1023. value =
analogRead(pin); // sets 'value' equal to 'pin' Note: Analog pins
unlike digital ones, do not need to be first declared as INPUT nor
OUTPUT.
analogWrite(pin, value) Writes a pseudo-analog value using
hardware enabled pulse width modulation (PWM) to an output pin
marked PWM. On Uno, this function works on pins 3, 5, 6, 9, 10, and
11. The value can be specified as a variable or constant with a
value from 0-255. analogWrite(pin, value); // writes 'value' to
analog 'pin' A value of 0 generates a steady 0 volts output at the
specified pin; a value of 255 generates a steady 5 volts output at
the specified pin. For values in between 0 and 255, the pin rapidly
alternates between 0 and 5 volts - the higher the value, the more
often the pin is HIGH (5 volts). For example, a value of 64 will be
0 volts three-quarters of the
-
6
time, and 5 volts one quarter of the time; a value of 128 will
be at 0 half the time and 255 half the time; and a value of 192
will be 0 volts one quarter of the time and 5 volts three-quarters
of the time. Because this is a hardware function, the pin will
generate a steady wave after a call to analogWrite in the
background until the next call to analogWrite (or a call to
digitalRead or digitalWrite on the same pin). Note: Analog pins
unlike digital ones, do not need to be first declared as INPUT nor
OUTPUT. delay(ms) Pauses a program for the amount of time as
specified in milliseconds, where 1000 equals 1 second. delay(1000);
// waits for one second millis() Returns the number of milliseconds
since the Arduino board began running the current program as an
unsigned long value. value = millis(); // sets value equal to
millis() Note: This number will overflow (reset back to zero),
after approximately 9 hours.
Serial.begin(rate) Opens serial port and sets the baud rate for
serial data transmission. The typical baud rate for communicating
with the computer is 9600 although other speeds are supported. void
setup() { Serial.begin(9600); // opens serial port } // sets data
rate to 9600 bps Note: When using serial communication, digital
pins 0 (RX) and 1 (TX) cannot be used at the same time.
2.1.3 ATMEGA 328 Features High Performance, Low Power AVR 8-Bit
Microcontroller Advanced RISC Architecture 131 Powerful
Instructions Most Single Clock Cycle Execution 32 x 8 General
Purpose Working Registers Fully Static Operation Up to 20 MIPS
Throughput at 20 MHz On-chip 2-cycle Multiplier High Endurance
Non-volatile Memory Segments
4/8/16/32K Bytes of In-System Self-Programmable Flash progam
memory 256/512/512/1K Bytes EEPROM (ATmega48P/88P/168P/328P)
512/1K/1K/2K Bytes Internal SRAM (ATmega48P/88P/168P/328P)
Write/Erase Cycles: 10,000 Flash/100,000 EEPROM Data retention: 20
years at 85C/100 years at 25C(1) Optional Boot Code Section with
Independent Lock Bits Programming Lock for Software Security
-
7
Peripheral Features Two 8-bit Timer/Counters with Separate
Prescaler and Compare Mode One 16-bit Timer/Counter with Separate
Prescaler, Compare Mode, and CaptureMode Real Time Counter with
Separate Oscillator Six PWM Channels 8-channel 10-bit ADC in TQFP
and QFN/MLF package 6-channel 10-bit ADC in PDIP Package
Programmable Serial USART Master/Slave SPI Serial Interface
Byte-oriented 2-wire Serial Interface (Philips I2C compatible)
Programmable Watchdog Timer with Separate On-chip Oscillator
On-chip Analog Comparator Interrupt and Wake-up on Pin Change
Special Microcontroller Features: Power-on Reset and
Programmable Brown-out Detection Internal Calibrated Oscillator
External and Internal Interrupt Sources Six Sleep Modes: Idle, ADC
Noise Reduction, Power-save, Power-down, Standby, and Extended
Standby
I/O and Packages: 23 Programmable I/O Lines 28-pin PDIP, 32-lead
TQFP, 28-pad QFN/MLF and 32-pad QFN/MLF
Operating Voltage: 1.8 - 5.5V for ATmega48P/88P/168PV 2.7 - 5.5V
for ATmega48P/88P/168P 1.8 - 5.5V for ATmega328P
Temperature Range: -40C to 85C
Speed Grade: ATmega48P/88P/168PV: 0 - 4 MHz @ 1.8 - 5.5V, 0 - 10
MHz @ 2.7 - 5.5V ATmega48P/88P/168P: 0 - 10 MHz @ 2.7 - 5.5V, 0 -
20 MHz @ 4.5 - 5.5V ATmega328P: 0 - 4 MHz @ 1.8 - 5.5V, 0 - 10 MHz
@ 2.7 - 5.5V, 0 - 20 MHz @ 4.5 - 5.5V
Low Power Consumption at 1 MHz, 1.8V, 25C for
ATmega48P/88P/168P:
Active Mode: 0.3 mA Power-down Mode: 0.1 A Power-save Mode: 0.8
A (Including 32 kHz RTC)
-
8
Pin diagram:
Pin Description :
VCC Digital supply voltage.
GND Ground.
Port B (PB7:0) XTAL1/XTAL2/TOSC1/TOSC2 Port B is an 8-bit
bi-directional I/O port with internal pull-up resistors (selected
for each bit). The Port B output buffers have symmetrical drive
characteristics with both high sink and source Capability. As
inputs, Port B pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port B pins are
tri-stated when a reset condition becomes active, even if the clock
is not running. Depending on the clock selection fuse settings, PB6
can be used as input to the inverting Oscillator amplifier and
input to the internal clock operating circuit. Depending on the
clock selection fuse settings, PB7 can be used as output from the
inverting Oscillator amplifier.
Port C (PC5:0) Port C is a 7-bit bi-directional I/O port with
internal pull-up resistors (selected for each bit). The
-
9
PC5.0 output buffers have symmetrical drive characteristics with
both high sink and source capability. As inputs, Port C pins that
are externally pulled low will source current if the pull-up
resistors are activated. The Port C pins are tri-stated when a
reset condition becomes active, even if the clock is not
running.
PC6/RESET If the RSTDISBL Fuse is programmed, PC6 is used as an
I/O pin. Note that the electrical characteristics of PC6 differ
from those of the other pins of Port C. If the RSTDISBL Fuse is
unprogrammed, PC6 is used as a Reset input. A low level on this pin
for longer than the minimum pulse length will generate a Reset,
even if the clock is not running. Shorter pulses are not guaranteed
to generate a Reset.
Port D (PD7:0) Port D is an 8-bit bi-directional I/O port with
internal pull-up resistors (selected for each bit). The Port D
output buffers have symmetrical drive characteristics with both
high sink and source capability. As inputs, Port D pins that are
externally pulled low will source current if the pull-up resistors
are activated. The Port D pins are tri-stated when a reset
condition becomes active,even if the clock is not running.
AVCC AVCC is the supply voltage pin for the A/D Converter,
PC3:0, and ADC7:6. It should be externally connected to VCC, even
if the ADC is not used. If the ADC is used, it should be connected
to VCC through a low-pass filter. Note that PC6..4 use digital
supply voltage, VCC.
AREF AREF is the analog reference pin for the A/D Converter.
ADC7:6 (TQFP and QFN/MLF Package Only) In the TQFP and QFN/MLF
package, ADC7:6 serve as analog inputs to the A/D converter.
These pins are powered from the analog supply and serve as
10-bit ADC channels.
2.2 Real time clock
Introduction
The real time clock (RTC) is a widely used device that provides
accurate time and date for many applications. The RTC chip present
in the PC provides time components of hour, minute and second in
addition to the date/calendar components of year, month and
day.
-
10
The RTC chip uses an internal battery that keeps the time and
date even when the power is off. One of the most widely used RTC
chips is the DS1307 from Dallas semiconductor.
Description
The DS1307 serial real-time clock (RTC) is a low power, full
binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM.
Address and data are transferred serially through an I2C,
bidirectional bus. The clock/calendar provides seconds, minutes,
hours, day, date, month, and year information. The end of the month
date is automatically adjusted for months with fewer than 31 days,
including corrections for leap year. The clock operates in either
the 24-hour or 12-hour format with AM/PM indicator.
The DS1307 has a built-in power-sense circuit that detects power
failures and automatically switches to the backup supply.
Timekeeping operation continues while the part operates from the
backup supply.
Fig: Pin configurations
Features:
Real-Time Clock (RTC) Counts seconds, minutes, hours, date of
the month, month, day of the week, and year with Leap-Year
Compensation valid up to 2100.
56-Byte, Battery-Backed, Nonvolatile (NV) RAM for Data Storage.
I2C Serial Interface. Programmable Square-Wave Output Signal.
Automatic Power-Fail Detect and Switch Circuitry. Consumes Less
than 500nA in Battery-Backup Mode with Oscillator Running. Optional
Industrial Temperature Range:-40C to +85C. Available in 8-Pin
Plastic DIP or SO. The DS1307 is a low-power clock/calendar with 56
bytes of battery-backed SRAM.
The clock/calendar provides seconds, minutes, hours, day, date,
month, and year information. The date at the end of the month is
automatically adjusted for months with fewer than 31 days,
including corrections for leap year.
The DS1307 operates as a slave device on the I2C bus. Access is
obtained by implementing a START condition and providing a device
identification code followed by a register address. Subsequent
registers can be accessed sequentially until a STOP condition is
executed. When VCC falls below 1.25 x VBAT, the device terminates
an
-
11
access in progress and resets the device address counter. Inputs
to the device will not be recognized at this time to prevent
erroneous data from being written to the device from an out-of
tolerance system. When VCC falls below VBAT, the device switches
into a low-current battery-backup mode. Upon power-up, the device
switches from battery to VCC when VCC is greater than VBAT +0.2V
and recognizes inputs when VCC is greater than 1.25 x VBAT.
Fig: Block diagram
Oscillator Circuit:
The DS1307 uses an external 32.768 kHz crystal. The oscillator
circuit does not require any external resistors or capacitors to
operate. The below table specifies several crystal parameters for
the external crystal. If using a crystal with the specified
characteristics, the startup time is usually less than one
second.
Parameter Symbol Min Typ Max Units Nominal frequency Fo 32.768
KHz Series Resistance ESR 45 K Load Capacitance CL 12.5 pF
Clock Accuracy: The accuracy of the clock depends upon the
accuracy of the crystal and the
accuracy of the match between the capacitive load of the
oscillator circuit and the capacitive load for which the crystal
was trimmed. Additional error will be added by crystal frequency
drift caused by temperature shifts. External circuit noise coupled
into the oscillator circuit may result in the clock running
fast.
-
12
RTC and RAM Address map: The table below shows the address map
for the DS1307 RTC and RAM registers.
The RTC registers are located in address locations 00h to 07h.
The RAM registers are located in address locations 08h to 3Fh.
During a multibyte access, when the address pointer reaches 3Fh,
the end of RAM space, it wraps around to location 00h, the
beginning of the clock space.
Clock and Calendar: The time and calendar information is
obtained by reading the appropriate register
bytes. Table 2 shows the RTC registers. The time and calendar
are set or initialized by writing the appropriate register bytes.
The contents of the time and calendar registers are in the BCD
format. The day-of-week register increments at midnight. Values
that correspond to the day of week are user-defined but must be
sequential (i.e., if 1 equals Sunday, then 2 equals Monday, and so
on.) Illogical time and date entries result in undefined operation.
Bit 7 of Register 0 is the clock halt (CH) bit. When this bit is
set to 1, the oscillator is disabled. When cleared to 0, the
oscillator is enabled.
It should be noted that the initial power-on state of all
registers is not defined. Therefore, it is important to enable the
oscillator (CH bit = 0) during initial configuration. The DS1307
can be run in either 12-hour or 24-hour mode. Bit 6 of the hours
register is defined as the 12-hour or 24-hour mode-select bit. When
high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is
the AM/PM bit with logic high being PM. In the 24-hour mode, bit 5
is the second 10-hour bit (20 to 23 hours). The hours value must be
re-entered whenever the 12/24-hour mode bit is changed.
When reading or writing the time and date registers, secondary
(user) buffers are used to prevent errors when the internal
registers update. When reading the time and date registers, the
user buffers are synchronized to the internal registers on any I2C
START. The time information is read from these secondary registers
while the clock continues to run. This eliminates the need to
re-read the registers in case the internal registers update during
a read. The divider chain is reset whenever the seconds register is
written. Write transfers occur on the I2C acknowledgement from the
DS1307. Once the divider chain is reset, to avoid rollover issues,
the remaining time and date registers must be written within one
second.
-
13
Table: Timekeeping registers Control Register
The DS1307 control register is used to control the operation of
the SQW/OUT pin.
Bit 7: Output Control (OUT) This bit controls the output level
of the SQW/OUT pin when the square wave
output is disabled. If SQWE = 0, the logic level on the SQW/OUT
pin is1 if OUT = 1 and is 0 if OUT = 0.
Bit 4: Square-Wave Enable (SQWE). This bit, when set to logic 1,
enables the oscillator output. The frequency of the
square-wave output depends upon the value of the RS0 and RS1
bits. With the square wave output set to 1Hz, the clock registers
update on the falling edge of the square wave.
Bits 1, 0: Rate Select (RS1, RS0). These bits control the
frequency of the square-wave output when the square-wave
output has been enabled. The following table lists the
square-wave frequencies that can be selected with the RS bits.
-
14
I2C DATA BUS The DS1307 supports the I2C protocol. A device that
sends data onto the bus is
defined as a transmitter and a device receiving data as a
receiver. The device that controls the message is called a master.
The devices that are controlled by the master are referred to as
slaves. The bus must be controlled by a master device that
generates the serial clock (SCL), controls the bus access, and
generates the START and STOP conditions. The DS1307 operates as a
slave on the I2C bus.
Fig: Data transfer on I2C Bus
Data transfer may be initiated only when the bus is not busy.
During data transfer, the data line must remain stable whenever the
clock line is
HIGH. Changes in the data line while the clock line is high will
be interpreted as control signals.
Accordingly, the following bus conditions have been defined:
Bus not busy: Both data and clock lines remain HIGH.
Start data transfer: A change in the state of the data line,
from HIGH to LOW, while the clock is
HIGH, defines a START condition.
Stop data transfer: A change in the state of the data line, from
LOW to HIGH, while the clock
line is HIGH, defines the STOP condition.
Data valid: The state of the data line represents valid data
when, after a START condition, the
dataline is stable for the duration of the HIGH period of the
clock signal. The data on the line must be changed during the LOW
period of the clock signal. There is one clock pulse per bit of
data. Each data transfer is initiated with a START condition and
terminated
-
15
with a STOP condition. The number of data bytes transferred
between START and STOP conditions is not limited, and is determined
by the master device. The information is transferred byte-wise and
each receiver acknowledges with a ninth bit. Within the I2C bus
specifications a standard mode (100 kHz clock rate) and a fast mode
(400 kHz clock rate) are defined. The DS1307 operates in the
standard mode (100 kHz) only.
Acknowledge: Each receiving device, when addressed, is obliged
to generate an
acknowledgement after the reception of each byte. The master
device must generate an extra clock pulse which is associated with
this acknowledge bit. A device that acknowledges must pull down the
SDA line during the acknowledge clock pulse in such a way that the
SDA line is stable LOW during the HIGH period of the acknowledge
related clock pulse. Of course, setup and hold times must be taken
into account. A master must signal an end of data to the slave by
not generating an acknowledge bit on the last byte that has been
clocked out of the slave. In this case, the slave must leave the
data line HIGH to enable the master to generate the STOP condition.
Depending upon the state of the R/W bit, two types of data transfer
are possible:
1. Data transfer from a master transmitter to a slave receiver:
The first byte transmitted by the master is the slave address. Next
follows a
number of data bytes. The slave returns an acknowledge bit after
each received byte. Data is transferred with the most significant
bit (MSB) first.
2. Data transfer from a slave transmitter to a master receiver.
The first byte (the slave address) is transmitted by the master.
The slave then
returns an acknowledge bit. This is followed by the slave
transmitting a number of data bytes. The master returns an
acknowledge bit after all received bytes other than the last byte.
At the end of the last received byte, a not acknowledge is
returned. The master device generates all the serial clock pulses
and the START and STOP conditions. A transfer is ended with a STOP
condition or with a repeated START condition. Since a repeated a
START condition is also the beginning of the next serial transfer,
the bus will not be released. Data is transferred with the most
significant bit (MSB) first.
The DS1307 may operate in the following two modes:
1. Slave Receiver Mode (Write Mode): Serial data and clock are
received through SDA (Serial data) and SCL (Serial
clock). After each byte is received, an acknowledge bit is
transmitted. START and STOP conditions are recognized as the
beginning and end of a serial transfer. Hardware performs address
recognition after reception of the slave address and direction bit.
The slave address byte is the first byte received after the master
generates the START condition. The slave address byte contains the
7-bit DS1307 address, which is 1101000, followed by the direction
bit (R/W), which for a write is 0. After receiving and decoding the
slave address byte, the DS1307 outputs an acknowledgement on SDA.
After the DS1307 acknowledges the slave address + write bit, the
master transmits a word address to the DS1307. This sets the
register pointer on the DS1307, with the DS1307 acknowledging the
transfer. The master can then transmit zero or more bytes of data
with the DS1307 acknowledging each byte received. The register
pointer automatically
-
16
increments after each data byte are written. The master will
generate a STOP condition to terminate the data write.
2. Slave Transmitter Mode (Read Mode): The first byte is
received and handled as in the slave receiver mode. However, in
this mode, the direction bit will indicate that the transfer
direction is reversed. The DS1307 transmits serial data on SDA
while the serial clock is input on SCL. START and STOP conditions
are recognized as the beginning and end of a serial transfer (see
Figure 5). The slave address byte is the first byte received after
the START condition is generated by the master. The slave address
byte contains the 7-bit DS1307 address, which is 1101000, followed
by the direction bit (R/W), which is 1 for a read. After receiving
and decoding the slave address the DS1307 outputs an
acknowledgement on SDA. The DS1307 then begins to transmit data
starting with the register address pointed to by the register
pointer. If the register pointer is not written to before the
initiation of a read mode the first address that is read is the
last one stored in the register pointer. The register pointer
automatically increments after each byte are read. The DS1307 must
receive a Not Acknowledge to end a read.
Fig: Data Write- Slave Receive mode
Fig: Data Read- Slave Transmit mode
-
17
Fig: Data Read (Write Pointer, Then Read)Slave Receive and
Transmit
2.3 Liquid crystal display
LCD stands for Liquid Crystal Display. LCD is finding wide
spread use replacing LEDs (seven segment LEDs or other multi
segment LEDs) because of the following reasons:
The declining prices of LCDs. The ability to display numbers,
characters and graphics. This is in contrast to
LEDs, which are limited to numbers and a few characters.
Incorporation of a refreshing controller into the LCD, thereby
relieving the CPU
of the task of refreshing the LCD. In contrast, the LED must be
refreshed by the CPU to keep displaying the data.
Ease of programming for characters and graphics.
-
18
These components are specialized for being used with the
microcontrollers, which means that they cannot be activated by
standard IC circuits. They are used for writing different messages
on a miniature LCD.
A model described here is for its low price and great
possibilities most frequently used in practice. It is based on the
HD44780 microcontroller (Hitachi) and can display messages in two
lines with 16 characters each . It displays all the alphabets,
Greek letters, punctuation marks, mathematical symbols etc. In
addition, it is possible to display symbols that user makes up on
its own. Automatic shifting message on display (shift left and
right), appearance of the pointer, backlight etc. are considered as
useful characteristics. Pins Functions
There are pins along one side of the small printed board used
for connection to the microcontroller. There are total of 14 pins
marked with numbers (16 in case the background light is built in).
Their function is described in the table below:
Function Pin
Number Name
Logic
State Description
Ground 1 Vss - 0V
Power supply 2 Vdd - +5V
Contrast 3 Vee - 0 Vdd
Control of
operating 4 RS
0
1 D0 D7 are interpreted as
commands
-
19
LCD screen: LCD screen consists of two lines with 16 characters
each. Each character consists of 5x7 dot matrix. Contrast on
display depends on the power supply voltage and whether messages
are displayed in one or two lines. For that reason, variable
voltage 0-Vdd is applied on pin marked as Vee. Trimmer
potentiometer is usually used for that purpose. Some versions of
displays have built in backlight (blue or green diodes). When used
during operating, a resistor for current limitation should be used
(like with anyLE diode).
D0 D7 are interpreted as data
5 R/W 0
1
Write data (from controller to
LCD)
Read data (from LCD to
controller)
6 E
0
1
From 1 to
0
Access to LCD disabled
Normal operating
Data/commands are transferred
to LCD
Data /
commands
7 D0 0/1 Bit 0 LSB
8 D1 0/1 Bit 1
9 D2 0/1 Bit 2
10 D3 0/1 Bit 3
11 D4 0/1 Bit 4
12 D5 0/1 Bit 5
13 D6 0/1 Bit 6
14 D7 0/1 Bit 7 MSB
-
20
LCD initialization
The initialization of LCD in Arduino programming is done by
including LiquidCrystal.h
header file. The statements for the LCD programming are as
following.
Description
The GRIET LCD shield has the following resources
2x16 LCD LM35 temperature sensor LDR(Light Dependent Resistor) 2
LEDs
The 2x16 LCD uses the 4-bit interface. The RD/WR pin of the LCD
is grounded so that write is permanently enabled. There is a
potentiometer the contrast. Adjust the pot till you see a strip of
dark blocks in the first line of the LCD. The LM35 is connected to
the A5 analog input pin of Uno. The LDR forms part of a potential
divider circuit whose output is given to A4 analog input pin of
Uno.
2.4 Relay
A relay is an electrically controllable switch widely used in
industrial controls, automobiles and appliances.
The relay allows the isolation of two separate sections of a
system with two different voltage sources i.e., a small amount of
voltage/current on one side can handle a large amount of
voltage/current on the other side but there is no chance that these
two voltages mix up.
-
21
Fig: Circuit symbol of a relay
Operation:
When a current flow through the coil, a magnetic field is
created around the coil i.e., the coil is energized. This causes
the armature to be attracted to the coil. The armatures contact
acts like a switch and closes or opens the circuit. When the coil
is not energized, a spring pulls the armature to its normal state
of open or closed. There are all types of relays for all kinds of
applications.
Transistors and ICs must be protected from the brief high
voltage 'spike' produced when the relay coil is switched off. The
above diagram shows how a signal diode (eg 1N4148) is connected
across the relay coil to provide this protection. The diode is
connected 'backwards' so that it will normally not conduct.
Conduction occurs only when the relay coil is switched off, at this
moment the current tries to flow continuously through the coil and
it is safely diverted through the diode. Without the diode no
current could flow and the coil would produce a damaging high
voltage 'spike' in its attempt to keep the current flowing.
Fig: Relay Operation and use of protection diodes
In choosing a relay, the following characteristics need to be
considered:
1. The contacts can be normally open (NO) or normally closed
(NC). In the NC type, the contacts are closed when the coil is not
energized. In the NO type, the contacts are closed when the coil is
energized.
2. There can be one or more contacts. i.e., different types like
SPST (single pole single throw), SPDT (single pole double throw)
and DPDT (double pole double throw) relays.
-
22
3. The voltage and current required to energize the coil. The
voltage can vary from a few volts to 50 volts, while the current
can be from a few milliamps to 20milliamps. The relay has a minimum
voltage, below which the coil will not be energized. This minimum
voltage is called the pull-in voltage.
4. The minimum DC/AC voltage and current that can be handled by
the contacts. This is in the range of a few volts to hundreds of
volts, while the current can be from a few amps to 40A or more,
depending on the relay.
Transistor driver circuit:
An SPDT relay consists of five pins, two for the magnetic coil,
one as the common terminal and the last pins as normally connected
pin and normally closed pin. When the current flows through this
coil, the coil gets energized. Initially when the coil is not
energized, there will be a connection between the common terminal
and normally closed pin. But when the coil is energized, this
connection breaks and a new connection between the common terminal
and normally open pin will be established. Thus when there is an
input from the microcontroller to the relay, the relay will be
switched on. Thus when the relay is on, it can drive the loads
connected between the common terminal and normally open pin.
Therefore, the relay takes 5V from the microcontroller and drives
the loads which consume high currents. Thus the relay acts as an
isolation device. Digital systems and microcontroller pins lack
sufficient current to drive the relay. While the relays coil needs
around 10milli amps to be energized, the microcontrollers pin can
provide a maximum of 1-2milli amps current. For this reason, a
driver such as a power transistor is placed in between the
microcontroller and the relay.
Fig. Block diagram of transistor driver circuit
Arduino Uno
Atmega328
A3
Vcc
Relay
Ground
-
23
The operation of this circuit is as follows: The input to the
base of the transistor is applied from the microcontroller port
pin
P1.0. The transistor will be switched on when the base to
emitter voltage is greater than 0.7V (cut-in voltage). Thus when
the voltage applied to the pin P1.0 is high i.e., P1.0=1
(>0.7V), the transistor will be switched on and thus the relay
will be ON and the load will be operated.
When the voltage at the pin P1.0 is low i.e., P1.0=0 (
-
24
lecture rooms, libraries, concert halls, meeting rooms, and
other places where silence is appreciated.
Mobile jammer is used to prevent mobile phones from receiving or
transmitting signals with the base stations. Mobile jammers
effectively disable mobile phones within the defined regulated
zones without causing any interference to other communication
means. Mobile jammers can be used in practically any location, but
are used in places where a phone call would be particularly
disruptive like Temples, Libraries, Hospitals, Cinema halls,
schools & colleges etc. Mobile Jammers were originally
developed for law enforcement and the military to interrupt
communications by criminals and terrorists to foil the use of
certain remotely detonated explosives. The civilian applications
were apparent with growing public resentment over usage of mobile
phones in public areas on the rise & reckless invasion of
privacy. Over time many companies originally contracted to design
mobile jammers for government switched over to sell these devices
to private entities.
As with other radio jamming, mobile jammers block mobile phone
use by sending out radio waves along the same frequencies that
mobile phones use. This causes enough interference with the
communication between mobile phones and communicating towers to
render the phones unusable. Upon activating mobile jammers , all
mobile phones will indicate "NO NETWORK" . Incoming calls are
blocked as if the mobile phone were off. When the mobile jammers
are turned off, all mobile phones will automatically re-establish
communications and provide full service. Mobile jammer 's effect
can vary widely based on factors such as proximity to towers,
indoor and outdoor settings, presence of buildings and landscape,
even temperature and humidity play a role.
The choice of mobile jammers are based on the required range
starting with the personal pocket mobile jammer that can be carried
along with you to ensure undisrupted meeting with your client or a
personal portable mobile jammer for your room or medium power
mobile jammer or high power mobile jammer for your organisation to
very high power military jammers to jam a large campuses Types of
jammers Pocket jammer Portable jammer Medium power jammer High
power jammer
Jamming devices overpower the cell phone by transmitting a
signal on the same frequency as the cell phone and at a high enough
power that the two signals collide and cancel each other out. Cell
phones are designed to add power if they experience low-level
-
25
interference, so the jammer must recognize and match the power
increase from the phone. Cell phones are full-duplex devices, which
mean they use two separate frequencies, one for talking and one for
listening simultaneously. Some jammers block only one of the
frequencies used by cell phones, which has the effect of blocking
both. The phone is tricked into thinking there is no service
because it can receive only one of the frequencies. Less complex
devices block only one group of frequencies, while sophisticated
jammers can block several types of networks at once to head off
dual-mode or tri-mode phones that automatically switch among
different network types to find an open signal. Some of the
high-end devices block all frequencies at once and others can be
tuned to specific frequencies.
To jam a cell phone, all you need is a device that broadcasts on
the correct frequencies. Although different cellular systems
process signals differently, all cell-phone networks use radio
signals that can be interrupted. GSM, used in digital cellular and
PCS-based systems, operates in the 900-MHz and 1800-MHz bands in
Europe and Asia and in the 1900-MHz (some times referred to as
1.9-GHz) band in the United States. Jammers can broadcast on any
frequency and are effective against AMPS, CDMA, TDMA, GSM, PCS,
DCS, iDEN and Nextel systems. Old-fashioned analog cell phones and
today's digital devices are equally susceptible to jamming.
Disrupting a cell phone is the same as jamming any other type of
radio communication. A cellphone works by communicating with its
service network through a cell tower or base station. Cell towers
divide a city into small areas, or cells. As a cell phone user
drives down the street, the signal is handed from tower to
tower.
A portable cell phone jammer featured by universal and handheld
design, could blocking worldwide cell phone networks within 0.5-10
meters, including GSM900MHz, GSM1800MHz, GSM850MHz/CDMA800MHz and
also 3G networks (UMTS / W-CDMA).
A mobile phone jammer is an instrument used to prevent cellular
phones from receiving signals from or transmitting signals to base
stations. When used, the jammer effectively disables cellular
phones. These devices can be used in practically any location, but
are
-
26
found primarily in places where a phone call would be
particularly disruptive because silence is expected.
Operation of jammer :
As with other radio jamming, cell phone jammers block cell phone
use by sending out radio waves along the same frequencies that
cellular phones use. This causes enough interference with the
communication between cell phones and towers to render the phones
unusable. On most retail phones, the network would simply appear
out of range. Most cell phones use different bands to send and
receive communications from towers (called full duplexing). Jammers
can work by either disrupting phone to tower frequencies or tower
to phone frequencies. Smaller handheld models block all bands from
800MHz to 1900MHz within a 30-foot range (9 meters). Small devices
tend to use the former method, while larger more expensive models
may interfere directly with the tower. The radius of cell phone
jammers can range from a dozen feet for pocket models to kilometers
for more dedicated units. The TRJ-89 jammer can block cellular
communications for a 5-mile (8 km) radius.
Actually it needs less energy to disrupt signal from tower to
mobile phone, than the signal from mobile phone to the tower (also
called base station), because base station is located at larger
distance from the jammer than the mobile phone and that is why the
signal from the tower is not so strong.
Older jammers sometimes were limited to working on phones using
only analog or older digital mobile phone standards. Newer models
such as the double and triple band jammers can block all widely
used systems (CDMA, iDEN, GSM, et al.) and are even very effective
against newer phones which hop to different frequencies and systems
when interfered with. As the dominant network technology and
frequencies used for mobile phones vary worldwide, some work only
in specific regions such as Europe or North America.
-
27
The jammer's effect can vary widely based on factors such as
proximity to towers, indoor and outdoor settings, presence of
buildings and landscape, even temperature and humidity play a
role.There are concerns that crudely designed jammers may disrupt
the functioning of medical devices such as pacemakers. However,
like cell phones, most of the devices in common use operate at low
enough power output (
-
28
should be as small as possible. As the equation shows, the
antenna pattern, the relation between the azimuth and the gain, is
a very important aspect in jamming.
Also as we know from Microwave and shown in the equation
distance has a strong influence on the signal loss. If the distance
between jammer and receiver is doubled, the jammer has to quadruple
its output in order for the jamming to have the same effect. It
must also be noted here the jammer path loss is often different
from the communications path loss; hence gives jammer an advantage
over communication transmitters. In the GSM network, the Base
Station Subsystem (BSS) takes care of the radio resources. In
addition to Base Transceiver Station (BTS), the actual RF
transceiver, BSS consists of three parts. These are the Base
Station Controller (BSC), which is in charge of mobility management
and signaling on the Air-interface between Mobile Station (MS), the
BTS, and the Air-interface between BSS and Mobile Services
Switching Center (MSC). The GSM Air-interface uses two different
multiplexing schemes: TDMA (Time Division Multiple Access) and FDMA
(Frequency Division Multiple Access). The spectrum is divided into
200 kHz channels (FDMA) and each channel is divided into 8
timeslots (TDMA).
Each 8 timeslot TDMA frame has duration of 4.6 ms (577
s/timeslot) [3]. The GSM transmission frequencies are presented in
Table 1
Frequency Hopping in GSM is intended for the reduction of fast
fading caused by movement of subscribers. The hopping sequence may
use up to 64 different frequencies, which is a small number
compared to military FH systems designed for avoiding jamming.
Also, the speed of GSM hopping is approximately 200 hops /s; So GSM
Frequency Hopping does not provide real protection against jamming
attacks.
Although FH doesnt help in protection against jamming,
interleaving and forward error correction scheme GSM Systems can
protect GSM against pulsed jamming. For GSM it was shown that as
the specified system SNR is 9 dB, a jammer min requires a 5 dB S/J
in order to successfully jam a GSM channel. The optimum GSM SNR is
12 dB, after this point the system starts to degrade.
GSM system is capable to withstand abrupt cuts in Traffic
Channel (TCH) connections. These cuts are normally caused by
propagation losses due to obstacles such as bridges. Usually
another cell could be used to hold communication when the original
BTS has disconnected. The GSM architecture provides two solutions
for this: first handover when the connection is still available,
second call reestablishment when the original connection
-
29
is totally lost. Handover decisions are made based on
transmission quality and reception level measurements carried out
by the MS and the BTS. In jamming situations call re-establishment
is probably the procedure the network will take in order to
re-connect the jammed TCH.
It is obvious that downlink jamming (i.e. Jamming the mobile
station handset'(receiver) is easier than uplink, as the base
station antenna is usually located far a way from the MS on a tower
or a high building. This makes it efficient for the jammer to
overpower the signal fro m BS. But the Random Access Channel (RACH)
control channels of all BTSs in the area need to be jammed in order
to cut off transmission. To cut an existing connections, the
jamming has to last at least until the call re-establishment timer
at the MSC expires and the connection is released, which means that
an existing call can be cut after a few seconds of effective
jamming.
The GSM RACH random access scheme is very simple: when a request
is not answered, the mobile station will repeat it after a random
interval. The maximum number of repetitions and the time between
them is broadcast regularly. After a MS has tried to request
service on RAC Hand has been rejected, it may try to request
service from another cell. Therefore, the cells in the area should
be jammed .In most cases, the efficiency of a cellular jamming is
very difficult to determine, since it depends on many factors,
which leaves the jammer confused.
Block diagram of Mobile Jammer
-
30
Design and implementation of mobile jammer: The block diagram of
mobile jammer consists of 4 main blocks. Those are Power supply
IF section
RF section
Antennas
Power Supply:
The mobile Jammer was designed for fixed use, and to take its
power from the regular 220V AC wall outlets. The IF & RF
sections of the jammer require +5V, +9Vand -9V dc. So a dc-dual
polarity power supply should be designed. The basic parts of power
supply are rectifier, filter and regulator. The rectifier converts
ac voltage to a pulsating dc voltage and can be either half wave
rectifier and full wave rectifier, the one we use here is the full
wave rectifier which has the advantage that it allows
unidirectional current to the load during the entire cycle of the
input voltage and the result of the full wave rectification is an
output voltage with a frequency twice the input frequency that
pulsated every half cycle of the input. The average value for a
full wave rectifier for a sinusoidal input is given by
The full wave rectifier used in the project is a full wave
bridge rectifier, which uses four diodes the peak output is given
by the, Where Vpsec is the output voltage across the secondary
winigng of the transformer .In the project the transformer used is
220/12,1.5A rating ,So Vavg=11V and Vp=15.88V.The second part of
the power supply is the filter which eliminate the fluctuations in
the output of the full wave rectifier so as to produce a constant
dc voltage ,the filter is simply a capacitor and its chosen to be
as large as possible to minimize voltage ripple in the output. The
final part of the power supply is the
-
31
regulator and it is used to provide the desire dconstant dc
output that is basically independent of the input voltage. Single
chip regulators were used to give
+5V, +9V and -9V dc voltages.Fig: 9.3 Circuit Schematic of the
power supply
Schematic Diagram Of Powersupply
If Section
The function of IF section of jammer is to generate tuning
signal for the VCO in the RFsection, which will sweep the VCO
through the desired range of frequencies. This tuning signalis
generated by a triangular wave generator along with noise
generator, and then offset by proper amount so as to sweep the VCO
output from the minimum desired frequency to a maximum.
Triangular Wave Generator:
To generator triangular wave we use 555 timer as a Astable
Multivibrator
-
32
The 555 timer consist basically of two comparators, a flip-flop,
a discharge transistor, and a resistive voltage divider. The
resistive divider is used to set the voltage comparator levels. A
555 timer connected to operate in the a stable mode as a free
running non sinusoidal oscillator, the threshold input is connected
to the trigger input. The external components R1,R2 and Cex forms
the timing circuit that sets the frequency of oscillation. The 0.01
uF capacitor connected to the control input is strictly for
decoupling and has no effect on the operation, in some cases it can
be left off. Initially when the power is turned on, the capacitor
Cex is uncharged and thus the trigger voltage(pin2) is at 0V.This
causes the output of the lower comparator to be high and the output
of the upper comparator to be low, forcing the output of the
flip-flop, and thus the base of Qd, low and keeping the transistor
off. Now, Cex begin charging through R1 & R2 (to obtain 50%
duty cycle, one can connect a diode parallel with R2 and choose
R2=R1). When the capacitor voltage reaches 1/3Vcc,the lower
comparator switcher to it slow output state, and when the capacitor
voltage reaches 2/3Vcc the upper comparator switches to its high
output state. This reset the flip flop causes the base of Qd to go
high, and turns on the transistor. This sequence creates a charge
path for the capacitor through R2 and the transistor, as indicated.
The capacitor begins to discharge, causing the upper comparator to
go low. At the point when capacitor discharge down to 1/3Vcc, the
lower comparator switches high, setting the flip flop, which makes
the base of Qd low and turns off the transistor. Another charging
cycles begins and entire process repeats the result is a
rectangular wave output whose duty cycle depends on the values of
R1 and R2, The frequency of oscillator is given by the following
formula.
Using the above equation for frequency equal 110KHz, one found
the values of R1, R2,and Cex. Then the output was taken from the
voltage on the external capacitor which has triangular wave form. A
simulation was done to verify the operation of circuit and the
output is shown in figure.
-
33
To avoid loading the timing circuit and changing the operation
frequency, the triangular wave on the terminal of the external
capacitor was buffered using op-amp
To achieve jamming a noise signal is mixed with the triangle
wave signal to produce the tuning voltage for the VCO. The noise
will help in masking the jamming transmission, making it look like
random noise to an outside observer. Without the noise generator,
the jamming signal is just a sweeping, unmodulated continuous wave
RF carrier.
White noise generator output spectrum
Signal mixer and DC-Offset circuits:
The triangle wave and noise signals are mixed using OP-Amp
configured as summer, then a dcvoltage is added to the resulted
signal to obtain the required tuning voltage using Diode-clamper
circuit. To gain good clamping the RC time constant selected so
that its more than ten times the period of the input frequency,
also a potentiometer was added to control the biasing voltage so as
to get the desired tuning voltage.
-
34
Op-Amp Summer Circuit
Rf Section
The RF-section is the most important part of the mobile jammer
it consist of the VoltageControlled oscillator(VCO),RF Power
amplifier ,and the antenna.These components wereselected according
to the desired specification of the jammer such as the frequency
range and the coverage range . Its important to note that all the
components used has 50 ohm input/output impedance, so 50 ohm
microstrip was needed for matching between the components. To
obtain the desired output jamming power for coverage range of 20m
first we found the jamming power required at the mobile receiver
Jr, knowing that SNRmin =9dB and Smax =-15dBm (i.e worst jamming
case).[5] then from SNRmin=S/J, where S=the signal power
Jr=-24dbm,then by invoking the free space path loss
equationF=32.45+20log(f*D),where Ds is distance in km and f is
frequency in MHz for 20 m the loss equals 58dB hence the jammer
should transmit a jamming signal with power equals
:58dBm-24dBm=34dBm,to sustain a 20m area.
-
35
Block diagram of IF section
Voltage controlled oscillator
The VCO is responsible for generating the RF signal which will
over power the mobile downlink signal. The selection of the VCO was
influenced by two main factors, the frequency of the GSM system,
which will be jammed and the availability of the chip. For the
first factor which implies that the VCO should cover the
frequencies from 935 MHz to 960 MHz , The MAX2623 VCO from MAXIM IC
was found to be a good choice , and fortunately the second factor
was met sequentially since MAXIM IC was willing to send two of the
MAX2623 for free.
Pin diagram of MAXIM
-
36
The MAX2623 VCO is implemented as an LS oscillator
configuration,integrating all tank circuit of the tank circuit
on-chip, this makes the VCO extremely easy-to-use , and the tuning
input is internally connected to the varactor as shown in figure
.The typical output power is -3dBm, and the output was best swept
over the desired range when the input tuning voltage was around 120
KHz.
MAXIM 2623 Pin connection
Features of VCO:
Fully Monolithic
Guaranteed Performance
On-Chip 50 Output Match
885MHz to 950MHz (MAX2623) +2.7V to +3.3V Single-Supply
Operation
Low Current Shutdown Mode
Smaller than Modules (8-pin MAX package) Pin description of
VCO:
1-NC- No Connection. Not internally connected. 2-TUNE-
Oscillator Frequency Tuning Voltage Input. High-impedance input
with a voltage input range of 0.4V (low frequency) to 2.4V (high
frequency) adjustment.
-
37
3-GND-Ground Connection for Oscillator and Biasing requires a
low-inductance connection to the circuit board ground plane.
4- SHDN-Shutdown Logic Input. A high-impedance input logic level
low disables the device and reduces supply current to 0.1A. A logic
level high enables the device
5- VCC-Output Buffer DC Supply Voltage Connection, bypass with a
220pF capacitor to GND for best high frequency performance
6 - VCC-Bias and Oscillator DC Supply Voltage Connection. Bypass
with a 220pF capacitor to GND for low noise and low spurious
content performance from the oscillator
7 -OUT Buffered Oscillator Output
8- GND-Ground Connection for Output Buffer. Requires a
low-inductance connection to the circuit board ground plane.
RF Power Amplifier:
To achieve the desired output power a gain stage was needed,
about searching for a suitable power amplifier it is cheaper to use
power amplifier from an old Mobile phones.ThePF08103b hitachi power
amplifier module from nokia mobile phone is sufficient to amplify
an input signal in the range 800MHz to 1 GHz by 34 dB.But in the
data sheet input should be1dBm.To meet this requirement we use
another power amplifier stage after vco and before hitachi power
amplifier .For this stage we use Mar-4SM power amplifier. The
MAR-4Sm has atypical gain of 8-dB for the frequencies range from dc
to 1GHz,so the output at this stage is around 5dBm.A typical
biasing configuration for MAR-4SM is shown in the figure
Now the power before the Hitachi RF power amplifier is 5dBm and
since 1dBm is required; so here we used 4dBm T-Network attenuator
as shown in the figure.
-
38
For a 4-dB attenuation and symmetric Network S12=S21=0.631And
for 50 ohms characteristic impedance we found the values of the
resistor using the following
equations,
Where X= (R2+50))//R3.
Antenna:
The most important part of any transmitter is the antenna. So a
suitable antenna should be selected .The antenna used in the
project is /4 wave monopole antenna and it has 50 Ohm impedance so
that the antenna is matched to the transmission system .Also this
antenna has low VSWR less than 1.7,and a bandwidth
-
39
of 150MHz around 916MHz center frequency which cover the mobile
jammer frequency range .The antenna gain is 2dBi.
-
40
Chapter 3
I2C COMMUNICATION
3.1 Introduction
IC ("eye-squared cee" or "eye-two-cee" Inter-Integrated Circuit,
generically referred to as "two-wire interface") is a multimaster
serial single-ended computer bus invented by Philips used for
attaching low-speed peripherals to a motherboard, embedded system,
cellphone, or other electronic device.
SMBus, defined by Intel in 1995, is a subset of IC that defines
the protocols more strictly. One purpose of SMBus is to promote
robustness and interoperability. Accordingly, modern IC systems
incorporate policies and rules from SMBus, sometimes supporting
both IC and SMBus with minimal reconfiguration required.
3.2 Design
IC uses only two bidirectional open-drain lines, Serial Data
Line (SDA) and Serial Clock (SCL), pulled up with resistors.
Typical voltages used are +5 V or +3.3 V although systems with
other voltages are permitted.
The IC reference design has a 7-bit or a 10-bit (depending on
the device used) address space.[5] Common IC bus speeds are the 100
kbit/s standard mode and the 10 kbit/s low-speed mode, but
arbitrarily low clock frequencies are also allowed. Recent
revisions of IC can host more nodes and run at faster speeds (400
kbit/s Fast mode, 1 Mbit/s Fast mode plus or Fm+, and 3.4Mbit/s
High Speed mode). These speeds are more widely used on embedded
systems than on PCs. There are also other features, such as 16-bit
addressing.
Note the bit rates are quoted for the transactions between
master and slave without clock stretching or other hardware
overhead. Protocol overheads include a slave address and perhaps a
register address within the slave device as well as per-byte
ACK/NACK bits. Thus the actual transfer rate of user data is lower
than those peak bit rates alone would imply. For example, if each
interaction with a slave inefficiently allows only 1 byte of data
to be transferred, the data rate will be less than half the peak
bit rate.
The maximum number of nodes is limited by the address space, and
also by the total bus capacitance of 400 pF, which restricts
practical communication distances to a few meters.
-
41
3.3 Reference design Therefore mentioned reference design is a
bus with a clock (SCL) and data (SDA)
lines with 7-bit addressing. The bus has two roles for nodes:
master and slave:
Master node node that generates the clock and initiates
communication with slaves Slave node node that receives the clock
and responds when addressed by the
master
The bus is a multi-master bus which means any number of master
nodes can be present. Additionally, master and slave roles may be
changed between messages (after a STOP is sent). There are four
potential modes of operation for a given bus device, although most
devices only use a single role and its two modes:
1. master transmit master node is sending data to a slave 2.
master receive master node is receiving data from a slave 3. slave
transmit slave node is sending data to the master 4. slave receive
slave node is receiving data from the master The master is
initially in master transmit mode by sending a start bit followed
by the
7-bit address of the slave it wishes to communicate with, which
is finally followed by a single bit representing whether it wishes
to write(0) to or read(1) from the slave.
If the slave exists on the bus then it will respond with an ACK
bit (active low for acknowledged) for that address. The master then
continues in either transmit or receive mode (according to the
read/write bit it sent), and the slave continues in its
complementary mode (receive or transmit, respectively).
The address and the data bytes are sent most significant bit
first. The start bit is indicated by a high-to-low transition of
SDA with SCL high; the stop bit is indicated by a low-to-high
transition of SDA with SCL high. All other transitions of SDA take
place with SCL low.
If the master wishes to write to the slave then it repeatedly
sends a byte with the slave sending an ACK bit. (In this situation,
the master is in master transmit mode and the slave is in slave
receive mode.)
If the master wishes to read from the slave then it repeatedly
receives a byte from the slave, the master sending an ACK bit after
every byte but the last one. (In this situation, the master is in
master receive mode and the slave is in slave transmit mode.)
-
42
The master then either ends transmission with a stop bit, or it
may send another START bit if it wishes to retain control of the
bus for another transfer (a "combined message"). IC defines basic
types of messages, each of which begins with a START and ends with
a STOP:
Single message where a master writes data to a slave; Single
message where a master reads data from a slave; Combined messages,
where a master issues at least two reads and/or writes to one
or
more slaves. In a combined message, each read or write begins
with a START and the slave
address. After the first START, these are also called repeated
START bits; repeated START bits are not preceded by STOP bits,
which is how slaves know the next transfer is part of the same
message.
Any given slave will only respond to particular messages, as
defined by its product documentation.
Pure IC systems support arbitrary message structures. SMBus is
restricted to nine of those structures, such as read word N and
write word N, involving a single slave. PMBus extends SMBus with a
Group protocol, allowing multiple such SMBus transactions to be
sent in one combined message. The terminating STOP indicates when
those grouped actions should take effect. For example, one PMBus
operation might reconfigure three power supplies (using three
different I2C slave addresses), and their new configurations would
take effect at the same time: when they receive that STOP.
With only a few exceptions, neither IC nor SMBus define message
semantics, such as the meaning of data bytes in messages. Message
semantics are otherwise product-specific. Those exceptions include
messages addressed to the IC general call address (0x00) or to the
SMBus Alert Response Address; and messages involved in the SMBus
Address Resolution Protocol(ARP) for dynamic address allocation and
management.
In practice, most slaves adopt request/response control models,
where one or more bytes following a write command are treated as a
command or address. Those bytes determine how subsequent written
bytes are treated and/or how the slave responds on subsequent
reads. Most SMBus operations involve single byte commands.
-
43
3.4 Timing diagram
3.5 Limitations The assignment of slave addresses is one
weakness of IC
Automatic bus configuration is a related issue. A given address
may be used by a number of different protocol-incompatible devices
in various systems, and hardly any device types can be detected at
runtime.
IC supports a limited range of speeds.
Devices are allowed to stretch clock cycles to suit their
particular needs, which can starve bandwidth needed by faster
devices and increase latencies when talking to other device
addresses. Bus capacitance also places a limit on the transfer
speed, especially when current sources are not used to decrease
signal rise times.
Because IC is a shared bus, there is the potential for any
device to have a fault and hang the entire bus.
Because of these limits (address management, bus configuration,
potential faults, speed), few IC bus segments have even a dozen
devices. It is common for systems to have several such segments.
One might be dedicated to use with high speed devices, for low
latency power management. Another might be used to control a few
devices where latency and throughput are not important issues; yet
another segment might be used only to read EEPROM chips describing
add-on cards (such as the SPD standard used with DRAM sticks). 3.6
IC (wire) library
This library allows you to communicate with I2C / TWI devices.
On the Arduino boards with the R3 layout (1.0 pinout), the SDA
(data line) and SCL (clock line) are on the pin headers close to
the AREF pin. The Arduino Due has two I2C / TWI interfaces SDA1 and
SCL1 are near to the AREF pin and the additional one is on pins 20
and 21.
-
44
Wire.begin()
Wire.begin(address) Descript ion Initiate the Wire library and
join the I2C bus as a master or slave. This should normally be
called only once.
Parameters
address: the 7-bit slave address (optional); if not specified,
join the bus as a master.
Returns None
Wire.requestFrom() Descript ion Used by the master to request
bytes from a slave device. The bytes may then be retrieved with the
available() and read()functions. As of Arduino 1.0.1, requestFrom()
accepts a boolean argument changing its behavior for compatibility
with certain I2Cdevices. If true, requestFrom() sends a stop
message after the request, releasing the I2C bus. If false,
requestFrom() sends a restart message after the request. The bus
will not be released, which prevents another master device from
requesting between messages. This allows one master device to send
multiple requests while in control. The default value is true.
Syntax Wire.requestFrom(address, quantity)
Wire.requestFrom(address, quantity, stop)
Parameters address: the 7-bit address of the device to request
bytes from quantity: the number of bytes to request stop :boolean.
true will send a stop message after the request, releasing the bus.
false will continually send a restart after the request, keeping
the connection active.
Returns byte : the number of bytes returned from the slave
device
-
45
Wire.beginTransmission(address) Descript ion Begin a
transmission to the I2C slave device with the given address.
Subsequently, queue bytes for transmission with the write()
function and transmit them by calling endTransmission().
Parameters address: the 7-bit address of the device to transmit
to
Returns None
Wire.endTransmission() Descript ion Ends a transmission to a
slave device that was begun by beginTransmission() and transmits
the bytes that were queued by write(). As of Arduino 1.0.1,
endTransmission() accepts a boolean argument changing its behavior
for compatibility with certainI2C devices. If true,
endTransmission() sends a stop message after transmission,
releasing the I2C bus. If false, endTransmission() sends a restart
message after transmission. The bus will not be released, which
prevents another master device from transmitting between messages.
This allows one master device to send multiple transmissions while
in control. The default value is true.
Syntax Wire.endTransmission() Wire.endTransmission(stop)
Parameters stop :boolean. true will send a stop message,
releasing the bus after transmission. false will send a restart,
keeping the connection active.
Returns byte, which indicates the status of the
transmission:
0:success 1:data too long to fit in transmit buffer 2:received
NACK on transmit of address 3:received NACK on transmit of data
-
46
4:other error
write() Descript ion Writes data from a slave device in response
to a request from a master, or queues bytes for transmission from a
master to slave device (in-between calls to beginTransmission() and
endTransmission()).
Syntax Wire.write(value) Wire.write(string) Wire.write(data,
length)
Parameters value: a value to send as a single byte string: a
string to send as a series of bytes data: an array of data to send
as bytes length: the number of bytes to transmit
Returns byte write() will return the number of bytes written,
though reading that number is optional
Wire.available() Descript ion Returns the number of bytes
available for retrieval with receive(). This should be called on a
master device after a call torequestFrom() or on a slave inside the
onReceive() handler. available() inherits from the Stream utility
class.
Parameters None
Returns The number of bytes available for reading.
-
47
read() Descript ion Reads a byte that was transmitted from a
slave device to a master after a call to requestFrom() or was
transmitted from a master to a slave. read() inherits from the
Stream utility class.
Syntax Wire.read()
Parameters none
Returns The next byte received
Wire.onReceive(handler) Descript ion Registers a function to be
called when a slave device receives a transmission from a
master.
Parameters handler: the function to be called when the slave
receives data; this should take a single int parameter (the number
of bytes read from the master) and return nothing, e.g.: void
myHandler(intnumBytes)
Returns None
Wire.onRequest(handler) Descript ion Register a function to be
called when a master requests data from this slave device.
Parameters handler: the function to be called, takes no
parameters and returns nothing, e.g.: void myHandler() Returns
None
-
48
Chapter 4 Block diagram and working 1. The project is specially
designed for Jamming the Signals. 2. Bridge type full wave
rectifier is used to rectify the ac Output of secondary of
230/12V step down transformer. 3. This voltage supply of 5volts
dc is given to the microcontroller ATmega 328. 4. We are
controlling this mobile jammer by means of a microcontroller. 5.
And also we are interfacing 16x2 LCD display to the microcontroller
to I/O ports. 6. The mobile jammer is interfaced to the controller
through relay by using a transistor
driver circuit.
Block Diagram 7. We are using Real time clock chip DS1307 is
used to set the schedule. 8. The activation and deactivation time
schedules can be programmed with
microcontroller and displayed on the LCD display. 9. The EEPROM
is used to store the predefined time schedules in it. 10. In this
project we use a HFD27/005-S relay for automatic switching. 11.
Here we are using 3control switches which are used to get the
cursor position on the
LCD, Increment and decrement switches for Increasing time,
decreasing time. 12. For the given pre-set time with the help of
the relay, Jammer is in ON condition and
hence blocks all the signals in the range of 860MHz 2170MHz.
-
49
Chapter 5 Flow chart
START
INCLUDE
ARDUINO FILES
INITIALIZE LCD MODULE
INITIALIZE I2C BUS
SET THE START AND STOP TIMES
IF (START TIME = =REAL TIME) ?
IF (START TIME
-
50
IF (STOP TIME = =REAL TIME) ?
JAMMER OFF JAMMER ON
-
51
chapter 6 Program Code
#include "Wire.h"
#include
#include
#include
byte SW0 = A0;
byte SW1 = A1;
byte SW2 = A2;
byte led = 13;
byte rly = A3;
LiquidCrystal lcd(12, 11, 4, 5, 6, 7);//GRRR int
hour,minute,second;
int ah1,am1,ah2,am2;
void setup() { pinMode(SW0, INPUT); pinMode(SW1, INPUT);
pinMode(SW2, INPUT); pinMode(led, OUTPUT); pinMode(rly, OUTPUT);
digitalWrite(led, LOW); digitalWrite(rly, LOW); lcd.begin(16,2);
digitalWrite(SW0, HIGH); digitalWrite(SW1, HIGH); digitalWrite(SW2,
HIGH);
-
52
ah1=(i2c_read(8)); am1=(i2c_read(9)); ah2=(i2c_read(10));
am2=(i2c_read(11)); lcd.setCursor(0,1); lcd.print(ah1);
lcd.print(':'); lcd.print(am1); lcd.print(" "); lcd.print(ah2);
lcd.print(':'); lcd.print(am2); } void loop() { printTime(); if
(digitalRead(SW0) != HIGH) { set_time(); // hold the switch to set
time } if (digitalRead(SW1) != HIGH) { set_alarm(); // hold the
switch to set ON Time & OFF Time } if(hour==ah1) {
if(minute==am1)
-
53
{ digitalWrite(led, HIGH); digitalWrite(rly, HIGH); } }
if(hour==ah2) { if(minute==am2) { digitalWrite(led, LOW);
digitalWrite(rly, LOW); } } } void printTime() { second =
RTC.get(DS1307_SEC,true); minute = RTC.get(DS1307_MIN,true); hour =
RTC.get(DS1307_HR,true); lcd.setCursor(0,0); lcd.print("TIME=");
lcd.print(hour,DEC); lcd.print(':'); lcd.print(minute,DEC);
lcd.print(":"); lcd.print(second,DEC); }
-
54
void set_time() { while (digitalRead(SW1) != 0) { if
(digitalRead(SW2) == 0) hour++;
if (hour > 23) hour = 0;
delay(200); lcd.setCursor(5,0); lcd.print(hour,DEC);
lcd.print(':'); } while (digitalRead(SW1) != 0) // set minutes { if
(digitalRead(SW2) == 0) minute++;
if (minute > 59) minute = 0;
delay(200); lcd.setCursor(8,0); lcd.print(minute,DEC);
lcd.print(':'); } RTC.set(DS1307_MIN,minute); //set the minutes
RTC.set(DS1307_HR,hour); //set the hours RTC.set(DS1307_SEC,0);
-
55
} void set_alarm() { while (digitalRead(SW0) != 0) // set hours
{ if (digitalRead(SW2) == 0) ah1++;
if (ah1 > 23) ah1 = 0;
delay(200); lcd.setCursor(0,1); lcd.print(ah1,DEC);
lcd.print(':'); } while (digitalRead(SW0) != 0) // set minutes { if
(digitalRead(SW2) == 0) am1++;
if (am1 > 59) am1 = 0;
delay(200); lcd.setCursor(3,1); lcd.print(am1,DEC); } while
(digitalRead(SW0) != 0) // set hours { if (digitalRead(SW2) ==
0)
-
56
ah2++;
if (ah2 > 23) ah2 = 0;
lcd.setCursor(7,1); lcd.print(ah2,DEC); lcd.print(':'); } while
(digitalRead(SW0) != 0) // set minutes { if (digitalRead(SW2) == 0)
am2++;
if (am2 > 59) am2 = 0;
lcd.setCursor(10,1); lcd.print(am2,DEC); } i2c_write(8,ah1);
//set the minutes i2c_write(9,am1); //set the hours
i2c_write(10,ah2); //set the minutes i2c_write(11,am2); //set the
hours } void i2c_write(byte baddr, byte data) {
Wire.beginTransmission(DS1307_CTRL_ID); Wire.send(baddr); // reset
register pointer Wire.send(decToBcd(data));
Wire.endTransmission();
-
57
delay(5); } byte i2c_read(byte baddr) {
Wire.beginTransmission(DS1307_CTRL_ID); Wire.send(baddr);
Wire.endTransmission(); delay(5); Wire.requestFrom(DS1307_CTRL_ID,
1); delay(5); byte data = bcdToDec(Wire.receive()); return
data;
} byte decToBcd(byte val) { // Convert normal decimal numbers to
binary coded decimal
return ( (val/10*16) + (val%10) ); } byte bcdToDec(byte val) {
// Convert binary coded decimal to normal decimal numbers
return ( (val/16*10) + (val%16) ); }
-
58
Chapter 7 APPLICATIONS AND ADVANTAGES
Applications
Application of mobile phone Signal Jammer In theory, the cell
phone signal jammer is applied to the place where are forbidden to
use mobile phones.
For example, cell phone signal jammers used in jails, prisoners
can be effectively prohibited contacting with the outside via
mobile phones and avoid the possibility of continued crime.
Cell phone jammers used in gas stations, can effectively avoid
the fire caused by using mobile phones.
Mobile phone jammers used in the military, can effectively
prevent leak important military secrets.
Mobile phone signal blocker used in the examination rooms, can
effectively prevent cheat through mobile communications.
Cell phone signal blocker used in schools, can assure students
to study without distraction and have a quiet rest.
Cell phone jammer used in theaters, can make everyone en- joy
the program without disturb.
Mobile phone jammer used in meeting rooms or training rooms, can
assure the effective of the meeting.
Mobile phone blocker used in cars, can effectively prevent the
GPS tracking ,etc . In fact, cell phone jammers is urgent needed in
jails.At present, all countries in the
world have regulations that forbidden use of mobile phones in
prison, but due to the defect of management, it's difficult to do
that.
In some countries such as Brazil in order to using cell phone
signal jammer in prisons even changed the law about forbidden to
use mobile phone jammers in their country.
Advantages
Easy to operate
Sophisticated security
Simple and Reliable Design
Sc