This is a read-write setting specifying the in-band signaling scheme used between the endpoints of a call on this VoIP peer, telling the router how to interpret ABCD signaling bits carried in the voice payload data, mirroring the ATM peer's equivalent object but for the IP network case. An admin configures this to keep supervisory signaling, like hook-flash and disconnect detection, working correctly when the call traverses this VoIP peer. For example, a mismatch in this setting between two interconnected gateways could cause a call to appear connected on the network layer while supervisory signals like disconnect are misread.