Bit robbing

Bit robbing: In digital carrier systems, the practice or technique of preempting, at regular intervals and for the purpose of transmitting signaling information, one digit time slot[?] that (a) is associated with the given user channel for which signaling is required, and (b) is used primarily for transporting encoded speech via that channel.

Note 1: Bit robbing is an option in networks compatible with T-carrier, e.g., an ISDN.

Note 2: In conventional T-carrier systems, bit robbing uses, in every sixth frame, the time slot associated with the least significant bit. Synonym speech digit signaling.

Source: from Federal Standard 1037C