Clear channel signaling is the ability to access telephony channels in the system and configure them to a user defined call control protocol, or to simply leave the lines 'clear'. The resources should have access to the telephony bus for media routing purposes, as well as signal detection, signal generation, and tone generation capabilities, if desired.
This common-channel signaling technique is also called the transparent mode for signaling. A single 64-Kbps channel (#24) is given up rather than 8 Kbps per channel for a robbed bit. In the T1 world, this means the primary rate interface (PRI) at 23B+D - simply stated, 23 bearer (B) channels at 64 Kbps clear channel, plus one data channel for signaling at 64 Kbps (D).