BCM Definition


A conversion device used to convert between voice signals encoded using adaptive differential pulse code modulation (ADPCM) and those encoded using pulse code modulation (PCM). As an ADPCM-encoded voice transmission generally is encoded at 32 kbps, two such signals can fit into a channel designed to support 64 kbps PCM-encoded voice.A BCM performs the necessary processing to pack two 4-bit ADPCM samples into a single 8-bit PCM time slot. Alternatively, a BCM can perform the necessary signal processing to convert an 8-bit PCM sample so that it will fit into a 4-bit ADPCM time slot. Such conversions are necessary when an E-carrier circuit supporting ADPCM channels connects to a central office (CO) exchange based on PCM, for example. A BCM generally is in the form of a printed circuit board (PCB) that fits into a standard time division multiplexer (TDM). See also ADPCM, encode, PCM, TDM, and time slot.

Webster's New World Telecom