railway communication prest
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07-10-2010, 05:37 PM
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RAILWAY COMMUNICATION PREST
Medium of Communications
Automatic Electronic Exchange
Railway has its own communication system including microwave stations and automatic electronic exchange.
C-Dot Electronic Exchange
It is an Indigenous SPC exchange developed by ﾓCenter for development of telemetricﾔ, C-DOT. C-DOT is developed on one microprocessor IC i.e. 65C02.
PSU-CardsIt is switch mode power supply card worked on -48±48 DC
Features of PSU-CardsIt feeds -48 V dc to subscriber line card and senses the flow of current in line.
If current is more than 10 mA and up to 35 mA max, it is treated that subscriber has lifted the handset.
If less than 10 mA the card treats as on the hook condition
PSU generates other supplies for various cards through dc to dc
SUBSCRIBER LINE CARD (SLC CARD)
There are 10 SLC cards. Each card contains 10 lines, there are 3 trunk cards, out of which 2 trunk cards can be replaced to 2 SLC cards.
TONE GENERATOR & DIAGNOSTIC CARD (TGD)
These cards generate 8 different tones to indicate different status of the subscriber line. It also has diagnostic circuit. TGD can diagnose the function of the card and give an error-reporting signal to TIC card. When it is required to feed a tone to subscriber, the time slot of particular tone is switched to time slot of the subscriber. Hence subscriber hears the tone.