Abstract: A performance monitoring arrangement conducts auxiliary in-band communications between a line interface unit and one or more channel units of a D4 channel bank without interrupting transmission of digital data to and from a customer premises. During a first, initialization mode of operation, and a second, smart performance-monitoring mode, the data communication format of a channel bank RNPCM bus is modified to allow insertion of an auxiliary line interface unit-sourced command bit between selected bits of the data. During the second mode of operation, the communication format of the channel bank link is further modified to provide for the transmission of the data at an increased data rate. This increased data rate permits a response message bit from the channel unit to be asserted on the RNPCM bus during a first time interval separate from that occupied by the increased rate data.

Abstract: A bleedover prevention circuit prevents a low data value of the last bit of an occupied channel unit time slot from bleeding over into the first and second bit times of an unoccupied channel unit time slot of a channel bank, by forcing the data lead to a high logic level within a terminal portion of the last bit time of an occupied channel unit time slot. The terminal portion of the last bit time occurs within a time interval delayed relative to a sampling clock edge, so that it does not detrimentally impact the validity of the value of the last data bit. If the immediately succeeding channel time slot is unoccupied, driving the data lead high prior to the beginning of such unoccupied channel time slot will render immaterial whether the last data bit value of the occupied channel time slot is a `one` or a `zero`, and will serve to effectively overcome the relatively long charging time, that would otherwise be required to pull the data lead high if the last data bit value were a `zero`.