mdf

Main distribution frame:-

M.D.F. is a media between switching network and subscriber’s line. It distribute wires in different areas and this wire connect switching room and subscribers line.

M.D.F. has different parts as:-

1. V.F. (Vertical frame) 2. N.E. (number of equipments)3. Module. 4. Selector. 5. Wire and Cable.

V.F. (Vertical frame):-

V.F. has distribution of wire in 10-10 horizontal sequence, left side connect with switching room and back side connect subscribers color wire. One V.F. has 100 pair of wire. Color wires connect with subscribers by grounding path. This color wire connects with pillar. Pillar has different no. of pair. It depends on phone connection in particular areas and after then pillar connect with D.P. (distribution point). Distribution point has 5-10 pair of wire. By the cable this one-one pair goes in the subscriber’s phone and 10 connections can connect with one D.P.

Figure: - Vertical Frame in M.D.F.

N.E. (Number of Equipment): -

N.E. frame is directly connected with switch room by this no. Find out the fault card of subscriber. Many time no. any fault in pillar pole and M.D.F. then find out the N.E. no of particular subscriber and check the fault. Card of switch room connection depends only on N.E. no means that with the N.E. no. check the reconnection between subscriber and M.D.F.

Figure: - N.E. in M.D.F

Module: -

Module is a medium, which connects M.D.F. CONNECTION OF N.E.from subscriber. It is a small hall. This module is present in V.F. is present in V.F. connect 100 module. No. of module is directly proportional to no. of pair.

Selector: -

In the M.D.F. department an important work is long distance communication. Many frames have many branches in different cities. For communication in modern banks, hotels, companies and their branches the help of modem is required. Selector is old manner but advance selector is a modem. Selector of old manner work by help of a worker. Main form call in main exchange and branch for communication.

In telephony, a main distribution frame (MDF or main frame) is a signal distribution frame for connecting equipment (inside plant) to cables and subscriber carrier equipment (outside plant). The MDF is a termination point within the local telephone exchange where exchange equipment and terminations of local loops are connected by jumper wires at the MDF. All cable copper pairs supplying services through user telephone lines are terminated at the MDF and distributed through the MDF to equipment within the local exchange e.g. repeaters and DSLAM. Cables to intermediate distribution frames terminate at the MDF. Trunk cables may terminate on the same MDF or on a separate trunk main distribution frame (TMDF). Like other distribution frames the MDF provides flexibility in assigning facilities, at lower cost and higher capacity than a patch panel. The most common kind of large MDF is a long steel rack accessible from both sides. On one side, termination blocks are arranged horizontally at the front of rack shelves. Jumpers lie on the shelves and go through a steel hoop to run vertically to other termination blocks that are arranged vertically. There is a hoop or ring at the intersection of each level and each vertical. Installing a jumper requires two workers, one on each side. The shelves are shallow enough to allow the rings to be within arm's reach, but the workers prefer to hang the jumper on a hook on a pole so their partner can pull it through the ring. A fanning strip at the back of the termination block prevents the wires from covering each others' terminals. With disciplined administration the MDF can hold over a hundred thousand jumpers, changing dozens of them every day, for decades without tangling. For the first half of the 20th Century, all MDF jumpers were soldered. This was reliable but slow and expensive. In the 1960s wire wrap was introduced, and in the 1970s punch blocks. Each jumper is a twisted pair. Middle 20th century jumper wires in the USA were 24 AWG single strand copper, with a soft polyethylene inner jacket and a cotton wrapper, impregnated to make it slightly brittle and easy to remove neatly. Late 20th century ones had a single, thicker coating of polyethylene, cross-linked to provide the correct degree of brittleness. Some urban central office MDFs are two stories high so they don't have to be more than a city block long. A few are three stories. By British custom the cables to the outside world are terminated on the horizontal side, and the indoors equipment on the vertical side. American usage is vice versa. Smaller MDFs, and some modern large ones, are single sided so one worker can install, remove or change a jumper. COSMOS and other computerized Operations Support Systems help by assigning terminals close to one another, so most jumpers need not be long and shelves on either type of MDF do not become congested. This database keeps track of all terminals and jumpers. In the early and middle 20th century these records were kept as pencil entries in ledger books. The later database method saves much labor by permitting old jumpers to be reused for new lines. The adoption of distributed switching in the late 20th century diminished the need for large, active, central MDFs. The MDF usually holds central office protective devices including heat coils and functions as a test point between a line and the office. Sometimes the MDF is combined with other kinds of distribution frame in a CDF The MDF in a private branch exchange performs functions similar to those performed by the MDF in a central office. In order to automate the manual jumpering the Automated Main Distribution Frame (AMDF) becomes an important role.

For smooth working of an exchange following unit are very important: -

1. Computer Unit: - it deals with additional services of the exchange to the customers with the help of computers.

2. Power Plant: - to feed proper power supply to exchange

3. AC Plant: - to maintain the continuous temperature + or – 2 degree Celsiusto the digital switch (exchange).

4. MDF: - to connect switch (exchange) with the external environment (Subscriber) i.e. it is the interface between subscribers and exchange.

1. Computer unit: -

As the name specified it is the main part of the exchange that deals with the all services provided by the exchange to the customers with the help of computer. It also provides the updated data to all other part of the exchange. The customers are using the services of the exchange by using the internet also gets connected to the main server present this room via an internet room. It mainly consists of the servers that are providing the different services.

The main servers of this room are:-

IVRS is used for the change number services provided by the exchange.

CERS are provided by the exchange to avoid the problems that the users arefacing the repairing of telephone. In this system when the user enters its complained it gets directly entered to the server and user is allotted with an id number.

LOCAL DIRECTORY ENQUIRY is another services provided by the exchange, by using this; subscribers calls the particular number and gets the directory enquiry. The server present in the main computer room provides this service.

INTERNET DIRECTORY ENQUIRY is the latest service by the exchange. In this type of service makes it enquiry using the internet, which gets connected to the main server at the internet room in the exchange and further to the main server in the computer room.

2. POWERPLANT: -

As we know that, the power is the main source or any organization. It is the case of E-10B exchange. That is the first requirement of any organization is the input. The main source of this exchange is AC supply. However, as soon as the power supply is gone off, then what is source? No one think on this that the telephone is always plays its role in the human life. Even if the power supply gone off. Thus there must be adjustment source of power.The main parts of the power room are: -

i. Batteries: -These are the instant sources of the power as soon as power is gone off. ii. Charging- Discharging Unit: -The batteries we are using in the power room need timely charging. As soon as the AC power supply is on, we make use of the charging unit present in the power room.

The slowly charging of the batteries is known as the trickle charging. But sometimes we need the BOOSTER charging. In this type of charging awe take of the batteries from the load and charge separately, until it gets fully charged. The main work of the discharging unit is to control the discharging of the batteries.

iii. Inverter and Converter Unit: -The main use of this system is to change AC mains to DC and vice versa as required by the parts of exchange.

iv. Engine Room:-We know that the batteries are the instant source of supply but we cannot use it for much larger time, thus for this, we have an engine to generate the power supply. They are of 885 KVA. Thus, this room controls the supply of the engine.

3. AC Plant (central air conditioner):-For the function of electrical equipment, cooling system is basic requirement.

The basic advantages of cooling systems are following:-

-It provides the thermal stability so that the temperature does not reach the tolerance limit of electronic equipment.

-It saves equipment from dust so to avoid malfunction of equipment’s.

-It protects equipment from excess humidity which can caused rusting of equipment.

The basic unit of measurement used in the industry is known as “ton ofrefrigeration”(TR) which is equivalent to the heat extracted in 24 hours for converting thousands kg of liquid to ice at zero degree. The compressor is the heart of the AC system and the costliest. It increases the pressure and temperature of the refrigerant gas coming from the evaporator coils by compressing it. Compressor comes in various types. The most widely used is simple reciprocal type a cylinder and piston arrangement. For capacity more than 120 TR, centrifugal compressors are used. The condenser liquefies the refrigerant gas by a heat exchange process. The capillary tube or the expansion valve pressurizes liquid refrigerant and meters it flows to the evaporator. The refrigerant then passes through the evaporator coils, which extract heat out ofthe ambience.

4. MAIN DISTRIBUTION FRAME

The primary function of MDF is: -

The fault of telephone number is removed in the MDF; it is called as Fault Remove Section. For removing the fault of telephone number, we use the testing these testing are T.T.Y. testing, Group testing, etc. For any type of testing firstly we need the vertical no. or the live tester, printer and computer test N.E. number of that particular telephone number. The telephone numbers are also disconnected in the MDF because of some specific reason.

➢ ORGANISATION OF THE MDF

PARTS OF THE MDF :-

1) Horizontal side 2) Vertical side 1) HORIZONTAL SIDE:-It is again subdivided in to two parts:-A) Exchange sideB) Line sideDescription of the horizontal side:-

RACK: - On the rack, the tags are situated. One rack is having eight Tags. The courting is done from up (0) to down (7).

TAG: - Each rack consists of eight tags.1 tag = 4 core1 core = 4 bunch1 bunch = 2 line

N.E.:- The word NE stands for the ‘NUMBER OF EQUIPMENT’. It is a 128 pair cable. The EWSD and MDF connected by NE.

WEDGE:-If we want to disconnect any two numbers then we insert a wedge between subscriber side and exchange side. Here wedge works as insulator made of plastic.

2) VERTICAL SIDE:-The vertical aside connected to the underground cable. This cable is having 100 pairs. These pair is distributed when we allot the telephone number to the subscriber.

Vertical side is again subdivided in two parts:-

One part is connected with the horizontal side and another with the Subscriber line by using 100 pair underground cable. This is how the present day telephone system works. Different exchanges have different architectures of switching call routing and other features.

FUNCTION OF MDF: -

• A fixed means of terminating the external cables.

• A means for mounting the protective devices for incoming circuits.

• A convenient point of interception for locating of faults.

• A means for cross connecting the external circuits to the appropriate Internal circuits. The MDF is properly earthed for the protection of the equipment. The external pairs are area wise terminated on the line side of the frame, while connection from the equipment is done on the exchange side in a numerical order. By interconnections at this frame with the help of jumper wires, any subscriber in any area can be given any exchange number. This MDF mounts Delay Fuses only.