Which digital signaling is correctly mapped to its functionality?
A. T1 PRI NFAS – Used to connect to the PSTN where caller ID is required and PRI is not an option
B. T1 CAS – Used widely in North America to connect to the PSTN or PBXs
C. T1 FGD – Uses a single D channel to control multiple spans of T1s with only B channels option
D. T1 and E1 PRI – Uses the Q Signaling variation of the basic ISDN specification
