Refers to the signaling mode of the port (or framer module). notApplicable(1)- means that no framer is needed for this port (no signaling), or that this object is not relevant. cas(2) means Channel Associated Signaling. Used for E1 Links. ccs(3) is the Common Channel Signaling (the signaling is not within the channels time slot - a TS for signaling is used). robbedBit(4) is a method implementing 7 bits for the voice and 1 bit dedicated for signaling. Used for T1 Links. other (5)- Signaling generally exists though not specifically according to one of the values listed ; this port uses a framer in this case.