Reduction of errors in D4 channel bank by multiframe comparison of transmit enable lead to determine whether analog channel unit is installed in D4 channel bank slot

摘要

The problem of digital data corruption heat occurs when an analog card is inserted into a card/time slot of a D4 channel bank is effectively remedied by sampling and analyzing the channel bank's transmit enable (TNEN) lead for successive frames of time slots. Unless analyzed TNEN lead samples of a channel unit time slot of interest derived over successive frames have the same logic state associated with an analog channel unit, the PCM data lead remains default-coupled to a digital data transmission lead. This prevents PCM-encoded spurious noise on the analog PAM lead from being erroneously asserted in place of serialized digital data bits that should have been passed directly from the digital data bus to the PCM bus.