Abstract: A channel monitoring system for monitoring a multiplicity of transmission lines including a plurality of channel monitors, a line assignment controller operative to determine a subset of the plurality of channel monitors to be assigned to monitoring an individual transmission line, an access switch operative, in response to an input from the controller, to connect the individual transmission line to the preferred number of monitors from among the plurality of channel monitors.

Abstract: In an adaptive differential PCM (ADPCM) system transmitter, three quantizers provide, respectively, 3, 4, and 5-bit quantization at the signal sampling rate. Each quantizer produces, in response to an input signal sample, a coded signal I(n) in the form of a bit sequence the number of bits in the coded signal from each quantizer being different. The number of bits comprising the coded signal is proportional to the bit rate. The bit rate can thus be altered by switching the codec output to selected ones of the adaptive quantizers. To eliminate quantizing distortion during bit rate transitions, one adaptive quantizer is caused to operate in the dominant mode, to receive the input signal sample and produce the coded signal I(n). At the same time, the other adaptive quantizers operate in a secondary mode to update their step-size .DELTA.(n) on the basis of the quantized signal produced by the dominant mode quantizer.