bit robbing - technical definition

Referring to the process in a channel bank or T1 time division multiplexer (TDM) whereby the least significant bit (LSB) in a byte is robbed and a signaling bit is inserted, thereby truncating the eight-bit voice sample to seven bits. Bit robbing does not affect the quality of pulse-code modulated (PCM) voice, as seven bits are quite satisfactory for reconstructing a high-quality approximation of the analog voice input, and the robbing occurs in only every sixth frame. (The LSB really is just fine-tuning of the voice signal, so to speak.) Bit robbing does, however, seriously impact other data types. As a result, data transmission in T-carrier networks is restrained to 56 kbps per channel. See also bit, byte, channel, channel bank, LSB, PCM, T1, T-carrier, and TDM.