What are the Telecom Systems in Indian Railways?

What are the Telecom Systems in Indian Railways? 

Telecom system in Indian Railways

a) Train Traffic Operating ckts(Block, IBS, LC gate ph, BPAC etc.)

b) Train Traffic Safety Communication (VHF, MTRC, TCAS)

c) Train Traffic Communication (Sec. Control, TPC, RC, TLC, ENGG,

Dy.Control, Hotline, Rly auto phone)

d) Data Circuits (UTS, PRS, FOIS, RAILNET, Data Loggers, PMS,

COA, ICMS, CMS)

e) Telephone Exchange (ISDN, VoIP)

f) Passenger Amenities (PA system, TIBs, CIBs, POET, ATVM,

Touch Screen KIOSK, Fare display board, BSNL phone)

g) Passenger Safety System (Surveillance System & Integrated

Security System - ISS)

h) Accident site Communication (ART, ARMV, V-SAT, WLL

Exchange, VHF,CUG)

i) Alternate Communication for Train Traffic Control (BSNL Phones,

CUG, 25W VHF, FWP)