ACKNOWLEDGEMENT We are greatly acknowledgement the role played by our concern teachers in the training of the fantastic PLCC. We are also very thankful to our Er. Kamal Bhalla of Communication department. We are also thankful to our training coordinator. Who provides us the opportunity to work on this PLCC. We gratefully acknowledge the debt which we owe to numerous authorities whose works writing we have consulted during the course of preparation of this training report. [1]
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ACKNOWLEDGEMENT
We are greatly acknowledgement the role played by our concern
teachers in the training of the fantastic PLCC.
We are also very thankful to our Er. Kamal Bhalla of
Communication department. We are also thankful to our training
coordinator. Who provides us the opportunity to work on this
PLCC. We gratefully acknowledge the debt which we owe to
numerous authorities whose works writing we have consulted
during the course of preparation of this training report.
Abstract[1]
The communication flow of today is very high. Many applications
are operating at high speed and a fixed connection is often
preferred. If the power utilities could supply communication over
the power-line to the costumers it could make a tremendous break-
through in communications. Every household would be connected
at any time and services being provided at real-time. Using the
power-line, as a communication medium could be a very cost-
effective way compared to other systems because it can use the
existing infrastructure, the electrical power distribution network,
Which is a ubiquitous one? In this report, we investigate the
applicability of power line communications technique to data
communications. The investigation is both theoretical and practical,
we detail on all aspects of power line carrier communications and a
Working power line link is designed and tested. Topics covered
include feasible applications of power line carrier communications
(hereafter referred to as PLCC), currently available protocols and
the impact of international standards.
[2]
CONTENTS
Chapter 1: Company Profile………………………….4
Chapter 2: Project Introduction…………………..…..9
Chapter 3: Network Architecture...................................15
Chapter4: System Description.........................................64
Conclusions………………………………………103
BIBLIOGRAPHY............................................….......104
[3]
CHAPTER 1
COMPANY PROFILE
1.1 Introduction:
With the arrival of 21st century the world has moved towards
another renaissance with communication technologies merging with
information technologies and in not so distant future with consumer
electronics.
PunCom is India's premier Telecom and IT equipment and solution
Provider Company having successfully supplied and implemented a
host of state-of-the-art Telecom, Software and integrated turnkey
solutions across the country. It is most sophisticated manufacturing
and software development facilities. It initially started of as a single
product venture, now has transformed into a multi product
company, manufacturing a wide range of sophisticated multiplexing
switches and transmission products providing total
telecommunication solution to customers. PunCom also offers a
wide range of software packages customized foe communication
products.
[4]
PUNCOM mission is to provide technologically superior products
and services of high quality on time cost effectively and
consistently to achieve investors and most important customer’s
confidence. Consistent track record of high productivity and its
strong financial position has made MNCS vie for equity at various
times.
1.2 Infrastructure:
North of New Delhi, located in garden state of Punjab, heartland of
Indian entrepreneurship, PunCom was established in July 1981, near
the city of Chandigarh. PunCom-SD is the largest software
development center in India. Starting its operation is a single rented
shed, now the company has 4 start-of-art factories spread over
17266 square of the land.
[5]
A 100 plus pool of qualified software professionals.
A diverse hardware platform range including Intel, HP and SUN.
Digital expertise on diverse software platforms.
1.3 Potential Venture in Technology:
PunCom’s mission is continuous advancement in the areas of
communication and information technology industry encompassing
telecommunication, software constancy, and voice processing.
PunCom has one of India’s most sophisticated manufacturing and
software development facilities. For this purpose, the manufacturing
facilities are equipped with the latest state-of-art machines like:
Automated SAD Assembly Lines.
Waves soldering Machines
Multiplayer PCB Assembly Lines.
Telecom Protocol Analyzer
[6]
1.6 Major Activities:
The Company has the following major areas of activities:
Manufacturing.
Equipment supply and after sales services.
System Design and engineering.
Education and turnkey Projects.
Survey, Installation commissioning and annual maintenances
contacts.
Research and development.
Training.
Constancy in System and network planning.
Customized software solution.
Switching products:[7]
Electronics private Automatics Branch Exchange with direct
Inward dialing facility.
Rural Automatics Exchange
Medium size Digital Exchange.
Large size Digital Exchange.
Remote Switching Units.
1.10 Key Activities:
Computational finance Computing.
System Software Solutions.
Hardware Solutions.
Mass Appeal Products.
Application Development Tools.
Web Applications.
Natural Language Processing Solutions.
1.11Turn-Key Products:
Mobile train radio for railway
[8]
Optical fiber and mobile radio for gas authority of India Limited
Microwave/UHF radio for DOT , railway , defense
Optical fiber system for railway
MAX-L digital exchange unto 3.5k capacities for DOT
CHAPTER 2
INTRODUCTION:
PL 9500 (Ver.-01) is a new generation Power Line Carrier
Communication (PLCC) equipment intended for transmission of
speech, facsimile, telegraphy, telemetry (RTU data) and Tele-
protection signals. It employs the carrier frequency range of 32
KHz to 508 KHz over High-voltage Overhead Power Transmission
lines with suitable line coupling equipment. Because of their low
attenuation in this carrier frequency range the transmission lines are
good means of communicating information over medium to long
distances.
The overall cost of the PLCC equipment is relatively low as
compared with other means of communication and is more cost
effective for long distance communications. The equipment
employs Amplitude Modulation Single Side Band Suppressed
Carrier (AM-SSB-SC) transmission to permit longer range of
transmission by optimum utilization of transmitted power and
frequency spectrum.
The equipment offers a single channel expandable to two channels.
Both the channels can be configured for full bandwidth speech/fax [9]
conversation or shared Speech-cum-Superimposed data channel or
one high-speed 4-Wire exclusive data channel of 1200 baud. The
equipment is also suitable for transmission of tele-protection
signals.
The terminal employs DSP techniques for full field
programmability and is thus flexible, easy to use and compact;
leading to simplified network design, installation and maintenance.
The equipment complies to the relevant ITU-T/CCITT, IEC 495:
1993-09 and IS 9482:1996-01 specifications ensuring reliable
coupling of channels at the VF interfaces in power system control
centers, power stations, microwave radio and leased backup links.
2.2 DOCUMENTATION
The documents for PUNCOM PLCC PL-9500 equipment are
intended to fully explicate the details of the Power Line Carrier
Communication Equipment and thus enable the users to fully
understand the system for proper utilisation and maintenance. To
achieve this, the documents have been divided in two categories as
shown below.
[10]USER MANUAL SERVICE MANUAL
DOCUMENTS
a) User Manual
This document is intended to provide the general understanding of
the system and an overview regarding its design and architecture.
For User Manual, the approach is to deal with highest level of
implementation and gradually move down to the basic building
blocks. Accordingly, a detailed network implementation is first
provided in the form of line diagrams and block diagrams. The
broad architecture of the system is then dealt with, duly explaining
the physical appearance and the basic block diagrams of the
constituents of the equipment. In order to provide all basic design
aspects, the technical specifications of the system have been given.
The document concludes with the explanation of the acronyms used
throughout the document.
b) Service Manual
[11]
Doc. no. PDC-TD-3.159 Doc. no. PDC-TD-3.160
Service Manual is provided for the convenience of the installation
personnel and maintenance/operating staff. All installation
procedures including mounting details and floor plan for the PLCC
rack along with the cabling scheme and user settings that are
required for the commissioning of the system have been duly
provided. Once commissioned, the system can be verified for
proper operation through user-friendly LCD screens and keypad.
Its details have been mentioned in terms of the operation of keypad
and meanings of messages on the display unit. Also, this document
contains regular checks for proper working and minor repairs and
adjustments in case of malfunctions. All the relevant information in
terms of preliminary adjustments for all the units and user settings
has been provided. Besides this, daily maintenance procedures and
service flow charts for all the units are provided so as to ensure
minimum failure time. This manual also contains the tables for the
frequency selection of the terminal and the tuning procedures for
the HF Tx and HF Rx filters.
2.3 SALIENT FEATURES
Single or dual channel configurations.
Terminal, Drop / Insert through coupled repeaters.
32 KHz to 508 KHz frequency range with 1 KHz frequency
allocation steps.
Power amplifier available for 20/40/80W PEP power output.
300 Hz to 3720 Hz Audio Frequency band.
[12]
Digital Signal Processing technique employed for easy field
programmability.
On site configuration of channel frequencies, transmission filters,
line impedance and speech, data and protection coupler levels.
Remote extension of direct EPABX line, Hot Line, Express
Channel and 2-Wire/4-Wire E&M modes available on VF Interface
unit.
Same Channel Modem for speech, fax & high speed RTU data.
Local and Remote loopback facility.
Fully complies with the relevant EMI and EMC standards.
Extensive use of Integrated Circuits and Crystal filters provides improved
quality and reliability of equipment.
Fully complies with IEC 495: 1993-09 and IS 9482:1996-01
Standards.
Supervisory unit facilitates easy maintenance and operation.
Easy user interface using LCD display for status and alarm
monitoring.
Protection from surge voltages and Lightning etc. is provided both
on VF side and HF side. Protection devices are in the form of Metal
Oxide Varistors for spike suppression and Gas Discharge Tubes to
counter the effect of Lightning etc.
Employs crystal band-pass filters giving extremely good VF
response.
Employs compressors and expanders to improve the noise
performance of the system.
[13]
2.4 APPLICATIONS
1. Full bandwidth (300 to 3400Hz), high quality speech cum fax
channels.
2. Data transmission at 1200bps; for Computer-Networking and
SCADA applications.
3. Wide selection of communication channels.
4. (i) Remote extension of telephone lines to distant/smaller
stations
- Subscriber mode.
- Exchange mode.
(This precludes the need to install ESLTR's at such stations)
(ii)2-Wire Hot line.
(iii) 4-Wire Express.
(iv) 2-Wire/4-Wire E&M junction circuits between two
exchanges.
(v) Service channel available on all these modes.
5. Drop/insertion of channels enroute allows through routing of end to
end channels (e.g. SCADA data and Hotline Speech channels on
through coupling (VF) and drop / insertion of dial up and
superimposed channels on VF basis. Dial up drop / insert channels
can be terminated on Integrated Local cum Transit PLCC switch
junction circuits.
[14]
Chapter-3
NETWORK ARCHITECTURE
3.1General:
The basic composition of a PLCC network and its interface to the
outdoor equipment viz., PABX and Power Line. As shown in the
figure, VFT data, RTU data etc. are directly fed to the PLCC
equipment and subscribers are fed to the PLCC on 4W/2W through
exchange. Subscriber can also be terminated directly on the PLCC
Equipment.
Fig:3.1:Network implemenatation of PUNCOM PL-9500 PLCC System.
[15]
3.2Implementation: Implementation of line traps and
coupling devices has also been shown. Protection couplers are
optional depending upon the requirements of the Customer. Fig:-
depicts the way voice connectivity is provided. Two
Configurations viz., Hotline and 4W E&M are shown in the figure
using Twin channel PLCC system.
Fig:-3.2:Link Implementation of PUNCOM PL-9500 PLCC showing Voice Connectivity
At the near end, i.e., Station A, in the Hotline mode, the subscriber
is directly connected to the PLCC and the other subscribers are
routed through 4W E and M from exchange. VF received at the
other end i.e., Station B, through High Voltage Transmission Line
is directly patched to the repeater terminal at VF level. At the far
end i.e., Station C the 4W E&M channel (Administrative channel) is
terminated at 4W E&M port of the exchange and hotline channel
[16]
is directly connected to the subscriber. This is an outline depicting
how a link is implemented in the field.
Fig: Depicts how RTU data is clubbed within the speech band
through RS232 interface provided on the RTU Data Modem.
It shows a PLCC link that carries both voice and data through a
repeater link.
Drop/Insert of Voice channel is achieved through a PABX
stationed at the receiver. Data is directly coupled by patching.
[17]
Fig:-3.3:Drop/Insert of voice channel; through-coupling of data
[18]
Fig:-gives the connectivity of the PLCC PL-9500 system with the
PABX. This can be implemented through Direct Exchange Lines,
which can either be 4W or 2W.
This is an advantage over the conventional PLCC systems where
the interconnectivity with the PABX is through 4W E and M
interface and ESLTRs are invariably required.
Fig:-3.4:Basic connectivity diagram for PUNCOM PL-9500 PLCC
[19]
3.3 SYSTEM CONFIGURATION:
PUNCOM's PLCC Terminal PL-9500 is a flexible system which can be
configured for single channel or twin channel operation. Both the
channels can be configured for full bandwidth speech/fax transmission or
shared Speech-cum- superimposed data channel or one high-speed 4-Wire
exclusive data channel of 1200 baud.
The single channel PL-9500 terminal is configured using the following:
Main Sub rack
a) VF Interface unit
b) Channel Modem unit
c) Data interface unit
d) Supervisory unit
e) Power Amplifier unit
f) Power Supply unit
[20]
HF Hybrid Sub rack
a) HF Filter Unit
b) HF Hybrid Unit
c) LCD and Keypad Unit (MTU)
Termination Panel
This configuration is shown in Fig.2.1 and Fig.2.2 for Single
terminal Single Channel and Two terminal Single Channel Systems
respectively. All units are same for 10W and 20W systems while
Power Amplifier Unit and Power Supply Unit are different for 40W
system.
For 10W/20W, PAMP-4 (Part no. AMP0697-1) and Power Supply
Unit type-1 (Part no. PU0742-1) are employed.
For 40W, PAMP-8 (Part no. AMP0697-8) and Power Supply Unit
type-2 (Part no. PU0742-2) are employed.
[21]
Fig.3.1 Single Terminal Single Channel System(10W/20W/40W)
[22]
Fig3.2 Two Terminal Single Channel System(10W/20W options only)
[23]
The twin channel PL-9500 terminal can be configured using the following:
1. Main Sub rack
a) VF Interface unit----2nos.
b) Channel Modem unit----2nos.
c) Data interface unit----2nos.
d) Supervisory unit
e) Power Amplifier unit
f) Power Supply unit
2. HF Hybrid Sub rack
a) HF Filter Unit
b) HF Hybrid Unit
c) LCD and Keypad Unit (MTU)
3. Termination Panel
All units are same for 10W and 20W systems while Power
Amplifier Unit and Power Supply Unit are different for 40W
system. [24]
For 10W/20W, PAMP-4 (Part no. AMP0697-1) and Power Supply
Unit type-1 (Part no. PU0742-1) are employed.
For 40W, PAMP-8 (Part no. AMP0697-8) and Power Supply Unit
type-2 (Part no. PU0742-2) are employed.
The PLCC PL-9500 rack can accommodate various configurations
on the basis of the HF output power they provide.
A 10W/20W system may be configured in any of the following.
Single Channel Single Terminal System.
Twin Channel Single Terminal System.
Two Single Channel Systems.
One Single + One Twin Channel System.
Two Twin Channel Systems.
A 40W system may be configured in the following two configurations
Single Channel Single Terminal System.
Twin Channel Single Terminal System.
[25]
Fig.3.3 Single Terminal Twin Channel System (10W/20W/40W)
[26]
3.4 CONFIGURATION DETAILS
Configuration: PLCC Rack
S.
NO.PART NAME / MODEL PART NO. FEATURES
1. 19” PLCC RACK RCK2531 Standard 19”
construction
Can house upto two
PLCC systems
2. 19” PLCC MAIN
SUBRACK
6U2533 Used for PLCC Main
rack.
Can provide single
channel or twin
channel operation.
3. 19” PLCC HF HYBRID
SUBRACK
3U2534-1 Used for HF Hybrid.
4. Alarm and Termination
panel
4U2532 Provides the user
termination for VF/Data
Circuits.
Displays Alarms.
[27]
Configuration: PLCC Main Sub Rack
[28]
[29]
S. NO. PART NAME / MODEL PART NO. FEATURES
1. VF INTERFACE UNIT VFJ0704 Provides voice interface.
2W/2W Hotline operation
4W/4W Express
2. DATA INTERFACE
UNIT-2.0Khz
DJU0700-1 Provides three data
channels with level
adjustment on individual
bases.
3. POWER AMPLIFIER-
40W(max.)
(PAMP-4)
AMP0697-1 Two stage amplifier.
10W/20W line Output
Power
4. POWER AMPLIFIER-
80W
(PAMP-8)
AMP0697-8 Two stage amplifier.
40W line Output Power
5. SUPERVISORY UNIT UP0726 Generates Local loop
and Remote loop
commands.
Monitors various alarms
Master Frequency
source.
6. POWER SUPPLY
UNIT-TYPE 1
PU0742-1 Used with PAMP-4.
7. POWER SUPPLY
UNIT-TYPE 2
PU0742-2 Used with PAMP-8.
8. CHANNEL MODEM
UNIT
CHM1020 AM-SSB-SC modulation.
Based on programmable
mixers for modulation
3.5 PLCC RACK:
The standard 19” mechanical construction practice has been used
for PL- 9500 rack. This is shown in Fig The PLCC rack of
2135mm(H) x 595mm(W) x 564mm(D) can accommodate two
numbers each of Main subrack, HF Hybrid subrack and Alarm &
Termination panel. Thus two systems can be equipped in the same
rack at repeater station for different directions eliminating the need
of extra space and hardware requirements. The face plans of
various possible configurations are shown in Fig.
PUNCOM standard rack conforms to DIN 19” standard and shall
accept equipment conforming to this standard.
Construction Aspects:
1. Front Door Aluminium extrusion frame with 3mm clear
perspex sheet fitted with gasket. Door is
provided with locking arrangement. Line
diagram of the section of the extrusion is shown
in Fig.2.5.
2. Rear Door Lockable rear door made of CR steel of
thickness 1.2mm. Gasket with Louvers are
provided at the bottom. Dust filters are
provided on the inner side of the louvers in
order to meet IP51 specifications.
3. Side Panels Made of CR steel of thickness 1.2mm. Louvers [30]
and air filter arev provided near the bottom.
Dust filters are provided on the inner side of the
louvers in order to meet IP41 specifications.
4. Top Cover Made of CR steel of thickness 2.0mm with side
vented slots. Rubber gromets are provided for
cable entry. No holes are provided on the top
cover in order that water droplets do not trickle
in from the top. This is in accordance with
IP51.
5. Bottom Cover Made of CR Steel of thickness 2.0mm; bottom
cover is provided with knockouts for cable
entry.
6. Frame Made of CR Steel of thickness 2.0mm. The
frame accepts rack mounting equipment
conforming to DIN19” standard.
7. Color Scheme Frame, Front Door - Structure Munshell N7
Side panels, rear door Top cover - Siemens
Grey
Bottom Cover - Zinc and passivation plating
[31]
Fig.3.4 PUNCOM PL-9500 PLCC RACK
[32]
Mounting Details and Floor Plan
The floor plan for installing the PLCC equipment is provided in
Fig. The PLCC racks should be secured to the ground before use.
Following methods can be used for fixing the rack.
Floor Mounting
Mark the front line to which the equipment front door should
match. The site be chosen in a way that atleast 770mm space is
available on both front and rear side for opening the doors and for
easy movement of the personnel. Mark four locations for mounting
as shown in Floor Plan. Drill four holes of size 20mm and depth
100mm at marked locations. Insert the rawl nuts (M12 size) in the
holes with the help of hammer. Place the Rack over the marked
area so as to match the rawl nuts with the holes provided at the
bottom of the rack. Tighten the rack with the help of bolts using a
suitable spanner (size20/21). Note that if cabling is to be done from
the bottom the equipment should be so placed that the knockouts on
the bottom plate fall on the trench. This approach is suitable only in
case the floor is concrete to the depth of the nut. In case where the
concrete depth is not adequate for fixing rawl nuts, a better
approach is to use the grouting bolts. For this, make four 100x100
mm square pits to a depth of 170mm at the four corners according
to the details given in Fig. Fix the grouting bolts in these pits and
fill these with cement / cement concrete. Accurately adjust the bolts
before the mixture settles and gets hardened. Lift the Rack and
place it over the marked area so as to match the bolts with the
[33]
holes provided at the bottom of the rack. Tighten the Rack with the
help of the nuts.
Rail Mounting
If the equipment is to be mounted on metallic rails ensure that the
distance between the mounting holes on rails is as shown in floor
plan. New holes should be drilled if the existing holes do not match
with floor plan. If it is not possible to drill matching holes in the
existing metallic rails, additional ironwork shall be installed to
enable drilling of the matching holes. Fix the rack over the rails
using M12 nut and bolt.
3.6 Main Subrack
The dimensions of Main sub rack are
Height 265.0mm
Width 483.0mm
Depth 260.0mm
Interconnections between the various units in the subrack are
through main motherboard, which contains the mating connectors
for all the units. Connections between the various sub racks are
made through 2 x 7 and D-type connectorised cables. On the
motherboard, all the HF connections between the sub racks are
through BNC connectorised coaxial cables.
[34]
The subrack can be configured for Single/Twin channel operation
by duplicating VF Interface unit, Channel Modem unit and Data
Interface unit. The front view of a fully equipped subrack for twin
channel operation is shown in Fig.2.7 for 40W and 20W options
respectively. Either of the channels can be configured for shared
speech cum superimposed data channel or high-speed exclusive
data channel. In case of superimposed data channel, Data Interface
unit is required to input or output VFT type data or RTU data. If
both channels are configured for superimposed data, two Data
Interface units (one per channel) are required.
Mechanical details
Standard subrack is shown in Fig. All the parts are discreetly shown on the Figure. It conforms to DIN/19” Standard.
The details of the subrack are given below.
i) Subrack 6U
Frame Height = 265mm
Width = 483mm
Depth = 260mm
[35]
Key Features
i) Made of Aluminum extrusions. Side panels made of
Aluminum sheet of thickness 2.5mm.
ii) Centre supporting extruded stiffener bar in 6U subrack for
supporting motherboard.
CONSTITUENT COLOUR
Frame White Alodined
Mounting Bracket Siemens’s Grey Powder Coated Semi
Gloss
Guide Rail Made of glass filled nylon (GFN) /
Noril FR Grade / Aluminium
Dimensions of Motherboard: Width: 426.72mm
Height: 261.85mm
Thickness:1.6mm
Dimensions of each card: Depth: 220mm
Height: 233.35mm
Thickness: 1.6mm
[36]
Fig.3.6 Front view of Main SubRack (40w & 20W
[37]
3.7 Constituents (Sub Units)
The details of the Front panels of different units that constitute the
Main Sub-rack are explained in the following sections.
VF Interface unit
VF interface unit provides interface between Carrier
Communication equipment and 2W/4W E&M PABX junctions.
Besides this, it offers Service telephone for maintenance purposes.
As shown in Fig.2.9, on the front panel of the VF Interface unit, 4
pin RTG test sockets are provided for 2W and 4W IN/OUT. Call
switch is provided for the purpose of Engineering Orderwire. The
details of the front panel components and the LEDs for alarms
provided on the front panel are given below.
S.No Designatio
n
Component Description
1. 4-Wire LED Indicates 4-Wire operation of the
VF Interface. Yellow LED normally
ON. OFF status indicates 2-Wire
operation.
2. BUZ LED Indicates Call Buzzer status. Red
LED normally OFF. ON status
indicates reception of call(ringing of
buzzer)
[38]
S.No Designatio
n
Component Description
3. JACK TEL LED Indicates Jack Telephone status.
Green LED normally OFF. ON
status indicates insertion of Jack
Tel. plug in its socket for call
initiation.
4. 4W IN RTG
Socket
Break plug for 4W VF transmit.
5. 4W OUT RTG
Socket
Break plug for 4W VF receive.
6. 2W RTG
Socket
Break plug for 2W VF
transmit/receive.
7. CALL SW
for Service
call
Push
buttonSwit
ch
Push button switch used to initiate a
service call.
8. JACK TEL 5-pin DIN
socket
This connector is used to insert the
Service telephone.
[39]
Fig.3.7 Front view of VF interface unit
[40]
Channel Modem unit
Channel Modem unit translates VF to HF using Amplitude modulation-single side band suppressed carrier technique. This is done by employing two stages of IF. The details of the signals extended on the front plate are provided below with reference to Fig.
Test points are provided for VF transmit/receive, PC IN/OUT and
Transmit/Receive Pilot. The details of the LEDs and other
components are provided below.
S.No Designation Component Description
1. Health LED Indicates Card health status.
Green LED normally blinking
indicates healthy condition.
Permanently ON/OFF indicates
faulty condition.
2. M Lead LED Indicates Tx signalling status.
Yellow LED normally ON. OFF
status indicates permanent GND
on M Lead Blinking status of the
LED indicates dialling on the
channel.
[41]
S.No Designation Component Description
3. Loop LED Indicates system in Local Loop
test mode. Yellow LED normally
OFF. ON status indicates system
in Local Loop.
4. E Lead LED Indicates Receive signalling
status. Yellow LED normally
ON. OFF status indicates
permanent GND on E Lead
Blinking status of the LED
indicates dialling on the channel.
5. AGC LED Indicates AGC loss condition.
Red LED normally OFF. ON
status indicates absence of
receive pilot i.e. AGC loss.
6. S/N LED Indicates status of signal to noise
ratio. Red LED normally OFF.
ON status indicates that S/N is
less than specified limits.
7. Muting LED Indicates status of carrier
generators. Red LED normally
OFF. ON status indicates PLL
failure of any carrier generator.
[42]
S.No Designation Component Description
8. XMT
ADJUST for
transmit lvl
Potentiomete
r
Used to fine adjust the transmit
VF level
9. RCV
ADJUST for
receive lvl
Potentiomete
r
Used to fine adjust the receive
VF level
10. VF XMT RTG St Break plug for VF transmit.
11. SID TX RTG St Break plug for SID transmit.
12. VF RCV RTG St Break plug for VF receive.
13. SID RCV RTG St Break plug for SID receive.
14. PC IN Test pt. Used to feed Protection Coupler
Send level for testing purpose.
15. TX PILOT Test pt. Used to monitor the Transmit
Pilot level.
16. PC OUT Test pt. Used to monitor the Receive
level at PC port.
17. RCV PILOT Test pt. Used to monitor the Receive
Pilot level.
[43]
Fig.3.8 Front view of Channel Modem Unit
[44]
Data Interface Unit
Data Interface unit provides the interface for three VF data
channels. The details of the front panel components are given in
Fig. and are described below.
S.
No.
Designatio
n
Component Description
1. TX1 RTG St. Used to feed the VF tone level
corresponding to data channel 1.
2. TX2 RTG St. Used to feed the VF tone level
corresponding to data channel 2.
3. TX3 RTG St. Used to feed the VF tone level
corresponding to data channel3.
4. RX1 RTG St. Used to check the received VF
tone level corresponding to data
channel 1.
5. RX2 RTG St. Used to check the received VF
tone level corresponding to data
channel 2.
6. RX3 RTG St. Used to check the received VF
tone level corresponding to data
channel 3.
[45]
Fig.3.9Front View of Data Interface Unit
[46]
Supervisory unit:
Supervisory unit monitors and controls the local and remote PLCC
terminals. It also monitors the alarms and displays them on the
LCD. The Front plate of Supervisory Unit houses alarm LEDs, test
tone generators and switches for loopback. These are described
below with reference to Fig.2.12.
Switches are provided for switching among channel 1 and
channel 2, and for achieving local loopback or remote loopback
for test purpose. The details of the LEDs are given below.
S.No Designation Component Description
1. Health LED Indicates supervisory health
status. Green LED normally
blinking. Permanent ON/OFF
indicates faulty condition.
2. Major Alarm LED Indicates major alarm condition.
Red LED normally off. ON
status indicates major alarm (link
failure).
[47]
S.No Designation Component Description
3. Minor Alarm LED Indicates minor alarm condition.
Red LED normally OFF. On
status indicates a minor alarm
though the link is through.
4. TM LED Indicates system in test mode.
Yellow LED normally OFF. ON
status indicates system in Local
Loop or Remote Loop.
5. ACO LED Indicates audio alarm cut off
status. Yellow LED normally
OFF. ON status indicates audio
alarm has been cut off.
6. ACO SW Push button
switch
Used to mute the audio alarm.
7. RESET Push button
switch
Used to reset the Supervisory
Unit.
8. CH1/CH2 Switch This switch is used to select
channel1 or channel2 for
loopback operation.
9. LL Push button
switch
This is used to initiate local loop
on selected channel
(Channel1/Channel2).
[48]
S.No Designation Component Description
10. RL Push button
switch
This is used to initiate remote
loop on selected channel
(Channel1/Channel2).
11. 153Khz Test pt. A test tone of 153Khz may be
extended from this test point to
the Power Amplifier unit
through patch cord.
12. 2W TONE RTG skt Used to provide Test tone on
2W.
13. 4W TONE RTG skt Used to provide Test tone on
4W.
14. SRL PORT 9-pin D-
conn.
This port is extended to connect
VT-100 Terminal.
[49]
Fig.3.10 Front view of Supervisory Unit
[50]
Power Amplifier unit
Power Amplifier amplifies the HF signal to be fed to the line in two
stages viz., Pre-amplifier stage and Power Amplifier stage. Two
different designs are provided – one to deliver a max. of 40W PEP
and the other 80W PEP.
The details of alarm LEDs and other front plate components are
provided as Fig and given below.
S.No Designation Component Description
1. PWR LED Power Supply input indication. Green
LED normally ON. OFF status
indicates loss of input supply.
2. O/P Mon LED Output level indication. Green LED
normally ON. OFF status indicates
output level is less than threshold
level.
3. Overload LED Output overload indication. Red LED
normally OFF. ON status indicates
power amplifier faulty condition.
4. RESET Switch Used to reset the Unit once the
overload condition disappears.
5. TEST INPUT Test pt This test point accepts the test tone of
153Khz from the Supervisory unit.
6. HF OUT BNC conn. Output of the amplifier used to feed
the HF signal to HF Filter.
[51]
Fig.3.11Front view of Power Amplifier Unit
[52]
Power Supply unit
Two types of designs for power supply are provided- one to be
employed for Power Amplifier delivering 40W/20W (40W max.)
and the other one to be employed for Power Amplifier delivering
80W. Front view of Power Supply Unit is shown in Fig.2.14.
Monitoring points are provided for all the input and output supply
voltages on the front panel. The details of the LEDs are given
below.
S.No Designation Compone
nt
Description
1. Power LED Indicates –48V present status.
Green LED, normally ON. OFF
status indicates absence of input –
48V.
2. I/P UV/OV
Alarm
LED Indicates –48V status. Red LED,
normally OFF. On status
indicates input –48V is not within
specified range.
3. O/P faulty LED Indicates the status of output
voltages. Red LED normally
OFF. On status indicates at least
one output is faulty or is out of
the specified range.
[53]
4. ON/OFF Switch Switches On or Off the Power
Supply Unit.
5. -48V/-48VRet Test pt. This test point is provided to
monitor the input supply voltage.
6. +36V/36V Ret
or
+50V/50V Ret
Test pt. Provided to monitor 36V output
supply voltage or 50V output
supply voltage.
7. +12V Test pt. Provided to monitor 12V output
supply voltage.
8. +5V Test pt. Provided to monitor 5V output
supply voltage.
[54]
Fig.3.12 Front view of Power Supply Unitt
[55]
3.8HF Hybrid Subrack
The HF Hybrid subrack shown in Fig. consists of HF Filter
module, HF Hybrid unit and LCD with Keypad. The HF Filter
module consists of two identical modules each having a PCB and
an air core inductor. Depending on the frequency band employed,
two kinds of HF Filter modules can be implemented. For high
frequency band from 100-508Khz, HF Filter(H) shall be used. For
low frequency band from 32-100Khz, HF Filter(L) shall be used.
These filters are field tuneable. The LCD and keypads provide an
easy interface to the user for maintenance and testing purposes.
Mechanical details
It conforms to DIN/19” Standard.
The details of the subrack are given below.
i) Subrack 3U:
Frame Height = 132.5mm
Width = 483mm
Depth = 260mm
[56]
Key Features
Made of aluminium extrusions. Side panels made of aluminium sheet.
CONSTITUENT COLOUR
Frame White Alodined.
Mounting Bracket Siemens’s Grey Powder Coated Semi
Gloss
Guide Rail Made of glass filled nylon(GFN)/Noril
FR Grade / Aluminium.
Constituents / Sub-units
HF Hybrid Unit Front view of HF Hybrid Unit is shown in Fig.. The details of the
alarms provided on the HF Hybrid Unit are given below.
S.No Designation Component Description
1. Line LED Output connected to line
indication. Green LED
normally ON. OFF status
indicates output of system is
not connected to LINE.
[57]
2. LOAD LED Output connected to dummy
load indication. Red LED
normally OFF. ON status
indicates output of system is
connected to dummy load.
3. MON Test pt. Used to monitor HF Tx level
and frequency across the
dummy load.
4. LINE/LOAD Switch Switches the system to Line or
Dummy load.
5. HF TX BNC conn. Accepts HF signal from HF
filter.
6. HF RCV BNC conn. Used to monitor HF signal
from HF hybrid to the Channel
Modem unit.
[58]
HF Filter
HF Filter is a bandpass filter of 4 KHz bandwidth, the frequency
selection for which can be done as required. Two different
modules are provided- one for lower frequency band (32-100
KHz) and one for higher frequency band (100-508 KHz).
HF IN port receives the output of Power Amplifier and gives out
filtered signal at HF OUT, which is fed to HF hybrid.
Fig.3.13Front view of HF Hybrid subrack
[59]
Fig.3.14 Front view of HF Hybrid Unit
2.3.6 Alarm and Termination panel
[60]
Alarm and Termination panel
The dimensions of the termination panel are
Height 177.0mm
Width 483.0mm
The front view of the Alarm and Termination Panel is shown in Fig.
The termination panel consists of Krone connector blocks, power &
alarm LEDs, MCB and HF break plugs. All the VF, data and
control signals accessible to the user are provided on the Krone
connector blocks.
Fi
g.3.15 Alarm and Termination Panel
[61]
Monitoring and Test Unit (MTU)
The operation of the PL-9500 is configurable and monitorable from
a LCD display and keypad provided on the front panel of the MTU.
Through this the user interacts with PL-9500 for the following
functions.
a) To display the status of the various alarms of the system.
b) To display as well as change the status of various loopbacks
on the system.
The LCD is a 16x2 character display based on English language or easy abbreviations are used in order to make it user friendly.
1. ENTER key[ ] This is used for the execution of the command being
cuurently displayed on the screen of the MTU.
2. UP arrow key[ ] This is used to scroll up to the previous menu.
3. DOWN arrow key[ ] This is used to scroll down to the next menu or next
item of the same menu.
4. LEFT and RIGHT arrow keys These are used to exit a particular mode of operation
once a prompt appears. These are used to scroll
through all the 16 characters of the line.
[62]
3.9 MAIN DISTRIBUTION FRAME :
In addition to the VF Termination Panel inside the rack, a separate
MDF with a maximum capacity of 100 pairs (MDF-01) or 200
pairs (MDF-02) is being provided for the applicable sites. MDF is
equipped suitably with multiple of 10 pairs termination blocks for
site-specific wiring requirements. The MDF has the provision for
IPM(Integrated Protection Module) on the required signals. The
line side terminations as well as the equipment side terminations
are on Krone type IDC connectors, facilitating easy
connection/disconnection as the case may be.
MDF is Wall-mountable type with lockable front door and a hinged
Termination Panel.
* MDF is not part of the PLCC Equipment supplied as per the
provisions in the Purchase Order
.
[63]
Chapter 4
SYSTEM DESCRIPTION
4 .1GENERAL DESCRIPTION:
System Block Diagram showing various modules is shown in Fig. 4.1.
The VF transmit section includes input circuits for different signals to be
transmitted. This includes speech, 64ynthesiz and pilot signal generation
circuit for 64ynthesiz and AGC purposes. On receive side the VF section
has compatible output circuits for separating out different signals from the
combined receive VF band. VF interface provides various speech
interfaces of 2-Wire line, 4-Wire Express circuit, 2-Wire/4-Wire E&M
PABX Junction circuits, Direct Subscriber (Telephone) Exchange Line
and Service Telephone.
The output of the VF Interface unit is fed to the Channel modem unit,
which comprises of VF, IF & HF sections for both transmit and receive
sides. The IF carrier of 4.896 MHz is generated in the terminal by a phase
locked loop crystal oscillator which converts VF transmit signal to a fixed
intermediate frequency band of 4KHz. Lower side band is filtered out
using a sharp cut off crystal band pass filter while the upper side band is
fed to the second modulator for translation to the required HF band. The
carrier of this modulator is the output of VCO 64ynthesized oscillator,
which can be programmed as per the output HF in the range of 32 KHz to
508 KHz with the help of 10-position DIP switches.
[64]
The receiver section takes the input from the programmable HF Rx Filter
and in this section, a VCO generates the required carrier using PLL
principle. After demodulation the resulting lower band is filtered out
using a crystal band pass filter while the upper band is demodulated to VF
using 4.896 MHz as the fixed carrier.
Pilot frequency is used for both AGC and supervision of the line. AGC is
built in the system to regulate the VF output for variations in the HF level.
The HF line section on transmit side has a Power Amplifier to provide
high power of transmission at terminal output followed by HF hybrid for
interfacing to 2-Wire High- Voltage line side. This section also includes
programmable filters on the transmit side to suppress the harmonics to
very low levels and to allow parallel connection of other PLCC terminals
on the same power line.
The basic function block diagram of PLCC terminal is shown in Fig.The
detailed block diagram of the PLCC terminal with various signal names
and interconnecting signals is shown in Fig.
[65]
Fig. 4.1 System Block Diagram
[66]
4.2SYSTEM FUNCTIONAL DESCRIPTION:
The system functional diagram in Fig.shows the basic blocks of
PUNCOM PLCC system. The termination panel houses the user interface
that includes VFT data, service telephone user controls etc.
All the speech signals are fed to the VF interface unit. This includes
service telephone. The unit converts all the speech into 4 wire for further
processing which is fed to the channel modem unit along with ‘M’ lead
signal. This voice band signal is converted to a 4Khz band in 32-508KHz.
Channel Modem Unit has the functional blocks for filtering and
modulation. VF is converted to HF in two stages of modulation. This
signal after conversion is fed to the Power Amplifier, filtered and passed
to HF Hybrid for transmission.
For Receive operation, HF signal is available at tag block from where it is
fed to channel modem through HF hybrid unit and HF Rx filter. This
signal is demodulated in two steps and passed to the VF interface unit.
Alarms from individual cards are extended to the supervisory unit to be
displayed on the LCD. These alarms indicate the presence/absence of
various cards; muting condition; S/N alarm etc. Loop back signals for
local and remote loopback are generated in the supervisory unit.
VFT data is converted to serial form by RTU Modem and fed to the data
interface unit, it can sum up the data from three different sources and then
feed it to the Channel Modem unit.
The details of various signals are provided in the descriptions of the
individual units give in section.
[67]
Allocation of Power to Speech and Data Channels
The scheme for allocating the weights to VF and data channels is
based on the noise bandwidth of each channel.
A 50B channel has a noise bandwidth of about 80Hz. Compared
with a 300-2400Hz-speech channel, the noise power level on a 50B
channel may be chosen 5 times lower.
Adjustment of Speech and Data Signal Levels
The absolute levels at the input of respective channel modem
should be according to the values.
To adjust the data levels, adjust the attenuator pads for respective
data channel in the data interface unit to match the levels provided
in the table above.
The strap settings for the attenuator pads is provided in the Service
Manual.
For speech, -16dBm level in channel modem is achieved with 12dB
pad setting in the VF interface unit.
[68]
4.3SUB-UNIT DESCRIPTION
The PLCC terminal PL-9500 consists of three subracks:
i) Main sub-rack
ii) HF Hybrid sub-rack
iii) Alarm and Termination panel
Main Subrack
It consists of the following units for a single channel system:
VF Interface unit
Channel Modem unit
Power Amplifier unit
Supervisory unit
Power Supply unit
Main Motherboard
Data Interface unit (Superimposed Data Multiplexer/De-
Multiplexer)
In order to equip the system for twin channel operation, one unit
each of VF Interface, data interface and Channel Modem is added
in the main subrack in the slots provided for the purpose.
[69]
VF Interface Unit:
General:VF Interface unit provides interface between carrier
communication equipment and 2-Wire/4-Wire E&M PABX
junctions, 2-Wire HOT LINE, 4-Wire EXPRESS circuits, REMOTE
SUBSCRIBER TELEPHONE, DIRECT EXCHANGE LINE (DEL),
Electronic four wire group selector (EFGS), etc.
In addition, it provides a Service Telephone interface for
Engineering Order-wire meant for maintenance purposes, the
hybrid control for permanent 4-Wire Express/4-Wire, tandem call
working and compander control. A buzzer has been built-in to
indicate Service call reception and to provide –48V for a remote 4-
Wire telephone set buzzer.
The unit has been provided with break/monitoring plugs and LED
indicators on front panel. There is also the provision for Loop tests
for maintenance and repair purposes.
Options/features with Functional details
2W / 2W hotline
As shown in Fig. 2W/2W hotline inputs are subjected to 4 Wire conversion through VF hybrid. 2W Tx path is normally through but can be changed over to 4W through a relay, which is normally de-energised. The attenuator in line can be selected to provide required levels for 2W and 4W tone.
For 2W hotline, on lifting the handset, the loop is closed. It is detected and ground potential is extended to M-lead. This makes the path through for 2W-subscriber side. Calling party is fed a ring back tone when E-Lead is ground. Lifting handset on called party
[70]
side initiates M-Lead and trips the ringer. E and M leads from PABX junction cause the signalling information to and reach the other end exchange.
4W E & M Mode
4W E and M mode operates with 4W trunk circuit of EPABX, in this 2W hybrid circuit is disabled and 4W speech IN and OUT are respectively routed to VF Tx and VF RCV of Channel Modem Unit through attenuators AT1 and AT2.
Engineering O/W
For Engineering O/W service call, attendant inserts the jack plug of handset to the corresponding socket. JACK TEL LED glows to indicate that Jack telephone is inserted. A 1Khz oscillator is provided to produce a tone, whenever call switch is pressed, which is transmitted through the 4W transmit path to the remote terminal. The tone is detected by the detector circuit, which operates the buzzer. Ring back tone is fed back to the calling side by the RBT generator. Inserting the jack telephone at the called end makes the call through.
4W Express Mode
For 4W express mode, 4W express telephone set operation is
similar to the functioning of the Engineering O/W except that the
operation is performed through 4W telephone set.
FXO / FXS Circuit (Remote subscriber exchange end)
FXO circuit is implemented for Direct-to-Exchange Line (DEL) operation. This circuit can be directly terminated to 2W exchange line and provides the function of Ring detect and battery feed.
FXS circuit is implemented for interface to the subscriber telephone. It provides the features of Loop detect and ring feed.
[71]
VF EQUALIZER:
VF Equalizer is provided in VF Rx path to compensate the amplitude distortion in VF band added by the line. During loop test equalizer should be set out of the circuit through header settings given in Service Manual
Control Signals (extended on termination panel)
Hybrid Control
This is used to select or remove the Hybrid on the Speech port. A
ground on this signal sets the interface in 4W mode and an open in
2W mode. This signal should only be used for E & M or 4W
Express mode and should be left open for Hotline and Remote
Subscriber modes.
Tandem Control
During transit control, ground is extended by the EPABX on
Tandem Control input which sets the interface for 4W operation.
Additionally, it removes the compander so that only one pair of
companders is active in the link.
[72]
Channel Modem Unit
General:-Channel Modem translates VF to HF in the range of 32-
508KHz. It houses its own carrier generators, Pilot, Signalling
circuit, Compander and AGC circuitry. This unit consists of two
parts one is main unit and other is the DSP based piggy back unit
called Transit Band Pass Filter and Pilot generator (TPG Board).
Functional blocks for filtering, modulation and translation of voice
frequency signals into Single Side Band Suppressed Carrier (AM-
SSB-SC) base band signals are provided in this card as its integral
unit.
As shown in Fig.Channel modem employs two stages of
modulation for conversion of VF signals to HF signal of 4 KHz
bandwidth in 32 to 508KHz. The VF signal of 4 KHz bandwidth is
first converted into a fixed intermediate frequency band of 4 KHz
using IF carrier of 4.896 MHz , obtained from a PLL Crystal
Oscillator. For second modulation stage a digital frequency
synthesiser is employed for generation of programmable carrier
frequencies to translate the VF band to HF band and vise-versa.
Because of 2-Wire working on HF side, transmit and receive
carriers are kept different. Carrier frequencies are synchronised
with a highly stable TCXO in the supervisory unit for better
frequency stability of the system.
[73]
The voice upper cut-off frequency can be selected from the
switched capacitor low pass filter in both transmit and receive
sections. Four different cut-off frequencies 2KHz / 2.2KHz /
2.4KHz / 3.4KHz can be selected through DIP Switches. The
programmability is achieved by changing the clock frequency fed
to the switched capacitor filter. The clock frequency is 200 times
the upper cut-off frequency of the required LPF.
Programmable pilot tone keyed by M Lead operation, generated in
the TPG board is used for link supervision, signalling and AGC,
same pilot can be used as the Guard signal for the teleprotection
equipment. The pilot frequency is programmable by DIP switches.
The available pilot frequencies are
2160/2220/2580/3360/3600/3660/3780 Hz 30 Hz. During the
signalling pilot frequency is shifted to pilot frequency + 30 Hz.
The terminal can provide various data channels for different baud
rates by selecting the programmable VF filters provided in Channel
Modem Unit. Optionally terminal can be configured to give
exclusive speech and data channels (1200baud). Baud rates are
selectable in the range 50-1200bps. The table below shows the
number of data channels supported for different baud rates.
[74]
Functional details
The channel modem functional blocks can be divided into following parts.
Transmit Side
VF signals are passed through a circuit consisting of gain control,
level adjustment and VF level limiting. To attenuate the low
frequency signals and equalise the transit frequency response near
300Hz, a high pass filter is provided. Compressor is used to
improve the signal to noise ratio for speech communication. Output
of the compressor is fed to the summer through Switched Capacitor
LPF, which attenuates VF signals above 2/2.2/2.4/3.4KHz. The
summer mixes the superimposed data, compressed speech and pilot
signalling, and the output of this is fed to the limiter and then to the
first transmit balanced modulator, hence converting it to IF of 4896
KHz. A crystal filter of 4896-4900 KHz pass band is used to pass
the upper side band. Output of this band pass filter is fed to the
second transmit modulator. The output of the second transmit
Carrier Generator (oscillator) is programmable in the range of 4392
KHz – 5100 KHz, thereby the HF (second oscillator – IF)
frequency can be programmed in the range of 32-508 KHz. The
upper side bands are undesired and are attenuated using a single
pole low pass filter before applying the HF signal to the HF
amplifier. Output of this HF amplifier is open collector and drives
an external 75ohm combining resistor in the shelf connector board.
[75]
Receive Side
Receive band limited HF spectrum containing a maximum of 2
channels from HF Hybrid card appears directly at Channel Modem
and is applied to the receive HF amplifier. This circuit provides
gain for the incoming signals and drives the first receive
demodulator. Crystal bandpass filter rejects all other frequencies
except the desired band of 4896 – 4900 KHz. Output of the crystal
bandpass filter goes to the IF amplifier which has built-in AGC
circuitry. Gain of the AGC amplifier is controlled by VAGC
available from TPG board. The output of AGC amplifier is fed to
second demodulator which gives VF output in 0 – 4 KHz range
after demodulation of the input signal with carrier frequency of
4896 KHz. Undesired upper side band is removed. Amplified VF
signal is fed to the switched capacitor low pass filter through
expander circuit. A low pass filter is used to prevent superimposed
data and pilot from appearing at the VF receive side. SID receive
signal is fed to the TPG board for taking out pilot and
superimposed data signal. The SID receive signal after filtration
through the programmable Transit Band Pass Filter appears as TBF
Out from TPG board and is fed to the Data Interface for further
communication to the RTU Data Modem.
[76]
Carrier Frequency Generation
Carrier generators serve as local oscillators for modulation. First
carrier generator is a PLL circuit generating 4896 KHz, used for the
first Transmit modulator and second receive demodulator. Second
programmable carrier generator is comprised of a programmable
digital synthesizer controlled by micro controller, used for the
second Transmit modulator and first receive demodulator.
Signaling Section
On the transmit side the pilot frequency of the channel is keyed by
the M Lead operation and on the receive side the signaling
information is retrieved by the TPG board and converted into a
logic to operate the relay connected to the E Lead
Switch Capacitor Low Pass Filter
Channel Modem uses the Switched Capacitor Filter Technique for
programmability of AF filters. Any of the four cutoff frequencies
2.0/ 2.2/ 2.4/ 3.4 KHz can be selected by selecting the DIP
Switches. Micro controller reads the switch setting and generates a
filter clock. It is 200 times the required cut off frequency and it
derives the switch capacitor filter chip to create the required low
pass filter.
[77]
Transit Band Pass Filter & Pilot Generator
This board is a piggy mount unit in the channel modem unit. This
generate the programmable pilot frequency and create signaling
information by FSK on receiving the pulses from the M Lead. On
receiver side it receives the SID-Rcv signal from the channel
modem and retrieves the pilot, which is used for the Automatic
Gain Control and link supervision. It also retrieves the signaling
information and converts it into a logic to operate the relay
connected to the E Lead. For superimposed data it has
programmable transit band pass filter whose upper and lower cut-
off frequencies are switch selectable in steps of 60Hz. The out put
of the TBF is fed to the data interface unit via motherboard.
Control signals (extended on Termination Panel)
PC-Control In/Out
This port is provided for Tele-protection signal. Normally a loop is
provided between these two signals. When the loop is removed,
speech, data, pilot and signalling channels are cut and full power is
allocated to PC IN (trip signal) sent by external Protection Coupler
Equipment.
PC IN
The trip signal (in the form of tones) is provided by the External
Protection Coupler Equipment on this input port. These signals are
[78]
sent on HF line at full power when ever a trip command is received
at the Protection Coupler.
PC OUT
The full speech band demodulated by the Channel Modem Unit is
fed to this port for sending to the External Protection Coupler
Equipment.
Power Amplifier Unit
General:-A detailed drawing showing the functional operation of
the Power Amplifier Unit Interface Unit is provided as Fig. Power
amplifier is used to amplify RF output from modem before it is
transmitted to the line. The amplifier PAMP4 and PAMP8 are
designed to deliver an output of 20W/40W and 80W PEP
respectively. Amplifier can be divided in three stages.
Pre Amplifier stage; Power Amplifier stage and the Control
section.
Functional Description
Pre Amplifier stage
This stage is used to drive the power amplifier stage. It has a
selectable gain. This section is further divided into two IC based
stages that operate on +12V. The output of this stage is coupled to
the Power Amplifier stage through a coupling transformer that
besides providing a gain of 3dB offers DC isolation between the
pre-amplifier stage and the power amplifier stage.
[79]
Power Amplifier stage
This stage is used to raise the levels of speech and other signals to
the required values for transmission over the line. Power amplifier
operates over a frequency range of 32-508KHz. This section is
further divided into two stages viz., differential amplifier stage and
the push pull power stage. The output of the push pull power stage
is coupled to the output transformer with the input impedance of
5.6 and output impedance of 75. This stage operates on
+36V(for PAMP4) and +50V(for PAMP8).
Control stage
This stage consists of the following sections:
Delay Circuitry:
It connects the output of the push pull power stage to the output
transformer after a delay of approximately 2sec once the system is
switched on. This enables the Power Amplifier to stabilize before it
is connected to the inductive load.
[80]
Power Level Detector section :
The output of the Power Amplifier is rectified and fed to the
supervisory unit which is further digitally processed and displayed
on the LCD.
Overload Alarm section:
In the event of line impedance mismatch or mishandling in the
field, the output of the power amplifier may increase drastically
resulting in the overload condition. To counter this, the gain of the
pre-amplifier section is reduced by 3dB and an alarm is extended to
the front panel of the Power Amplifier. This condition may be reset
using Reset switch provided on the front panel.
Data Interface Unit
General:-A detailed drawing showing the functional operation of
the Data Interface Unit is provided as Fig.3.11. The unit comprises
of Superimposed Data Multiplexer & De-Multiplexer and Transit
Band-Pass filter. The unit is provided with loop back facility for
remote end testing on generation of remote loop back command
from the supervisory unit. Data interface card interfaces with the
modem on 4W interface. The card can provide upto three
multiplexed and three demultiplexed VF channels for data
communication.
[81]
Functional details
Transformers in the data path provide for isolation and impedance
matching. The data is combined by the combiner and transferred to
channel modem unit as SID-TX (Trans superimposed data).
Superimposed receive data (SID-RCV) from channel modem is
decombined to give data at three output ports of the Data Interface
Unit.
In case more data channels are to be equipped, they can be
implemented with the help of a separate Combiner/Decombiner
Unit which can provide 5 data ports when put on any of the
existing data channels. The inputs and outputs of this unit are
transformer-coupled. This unit occupies 1U space and may be
equipped in any of the 1U slots. Further these units may be
cascaded to increase the number of data channels available. On
transmit side, individual channel levels can be adjusted.
[82]
Supervisory Unit
General:-A detailed drawing showing the functional operation of
the Supervisory Unit is provided as Fig. The supervisory unit is
provided to control and monitor local and remote PLCC terminals.
It monitors all the alarms generated in the system and displays the
status of the alarms on the LCD.
The local loop and the remote loop test commands can be generated
from the supervisory unit. Supervisory also displays the minor and
major alarms in case of system fault.
A highly stable TCXO is also provided in this card to synchronise
various oscillators in the system. Two test tone generators of 800
Hz and 153 KHz are provided for testing purposes.
Functional details
Input ports
Input ports are provided to monitor the system status and alarms
One input port is reserved for the system ID and one for
configuring the system.
[83]
Output ports
Output ports are provided for issuing the loopback commands for
any of the two channels or for indicating various alarm conditions.
ADC section
ADC section converts the various analog signals e.g. AGC level,
output power level and power supply voltages in the digital form to
be displayed on the LCD.
DTMF Transceiver section
This section issues the command for remote loop and also detects
the remote loopback command at the remote end.
RS 485/RS 422 Port
The serial port can be configured either by software or hardware
for RS422 or RS485 operation. In case of RS422 operation, the
system can be configured as master or slave. This port can be used
to patch the supervisory data from two or more PLCC Terminals at
a place. This port interfaces with the microcontroller through an
external DUART.
RS 232 Port
This is provided to monitor the status of the equipment at Local or
Remote ends. This port may also be used to download the new
version of the software.
[84]
Test tones
153 KHz tone
A test tone of 153KHz is extended on front plate of the Supervisory
Unit and this may be fed to the Power Amplifier Unit through
patch cord to carry out the functional checks of Power Amplifier
Unit. Channel modem is jacked out whenever this test tone is fed to
the power amplifier unit. This is a square wave and provides an
output rich in harmonics. Injection of this test tone should result in
glowing of O/P Mon LED on Power Amplifier front panel.
800 Hz tone for 2W/4W
A test tone of 800Hz (sinusoidal) is extended on the front panel of
the Supervisory Unit on RTG socket. This is transformer coupled
and may be fed to VF Port in loopback mode or otherwise through
RTG cable. The results may accordingly be noted on the 4W/2W
ports (in loopback mode) or HF port. When operated in 2W mode,
the setting in the VF interface unit should correspond to 2W.
Power Supply Unit
A detailed drawing showing the functional operation of the Power
Supply Unit is provided as Fig.3.13. Power Supply Unit is a SMPS
card, which converts –48VDC input (-40VDC to –60VDC range) to
[85]
+ 36V(+50V) for power amplifier and + 12V & 5V for operation of
other cards of PLCC.
Power Supply unit works in flyback conversion mode. It has two
pulse width modulator (current mode) chips IC3842. One chip is
used for +36V & -36V(+50V and –50V) and the other chip for
+12V, -12V & 5V.
Input circuitry consisting of EMI/RFI filter offers common mode
rejection and provides attenuation at frequencies above 40KHz.
Output of filter drives power switching transformer. Switching
pulses of controlled duty cycle drive the power MOSFET i.e.
energy is forwarded through the primary winding by switching at
frequency of 40KHz. Control circuit consists of PWM chip 3842. It
varies the duty cycle i.e. switching of the power MOSFET
according to the output voltage +36V. If the output voltage tries to
increase, PWM chip senses the voltage through optocoupler and
decreases the duty cycle thereby decreasing the voltage and vice-
versa (i.e. If output voltage tries to decrease).
Transformer stores energy during on period and pumps energy in
the secondary during off period. Secondary voltages are rectified by
diode/capacitor combination and then filtered through on an
additional L-C filter combination.
The same circuit applies for + 12 & +5V. The feedback is sensed
through -12V output and +12V is regulated with the help of low
drop out regulator & +5V is regulated with the help of fixed
regulator.
[86]
-48V after filtering through EMI/RFI filter is given for ringer
circuit.
Main Motherboard
All the interconnections of signals on various cards are achieved by
means of PCB mounted on the shelf back. All the connections to
the Termination Panel from the motherboard are made by means of
2 x 7 connectorised cables. Interconnections between various
subracks are through BNC and Molex connectorised cables.
Standard Euro connectors are used for firm insertion of cards. To
avoid insertion of card in wrong slot, interlocking is provided on
the motherboard as well as on critical cards. This is achieved by
varying the positions of the connectors on these cards and on the
corresponding slots on the motherboard.
HF Hybrid Subrack
This subrack consists of the following units:
i) HF Filter module
ii) HF Hybrid unit
iii) LCD with Keypad
iv) HF Hybrid motherboard
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CONCLUSION
The power line was never intended for communications
purposes. PLC device has limited use because of strong
interference, varying attenuation and impedance problems.
The PLCC system designer is limited in the bandwidth
available for communications not only by physical
properties of the power line, but also by regulatory
standards imposed by governing bodies. But the
applicability and the benefits of this technology are so
significant that, armed with many modern communications
techniques, and with careful thought, these challenges can
be definitely overcome.
BIBLIOGRAPHY
http://www.puncom.com
http://www.wifinotes.com
http://www.electronicsforu.com
[88]
http://www.howstuffworks.com
http://www.sciencefair.com
http://www.technologiestoday.com
http://www.google.com
Manual of Power Line Carrier Communication.
[89]
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