Adaptive no balance DX signalling circuit

摘要

The no balance duplex signalling circuit eliminates the need for setting balance resistors and capacitors to match or be proportional to cable resistance and capacitance as was required of previous duplex signalling circuit designs. A microcomputer is also used to evaluate the output of a simple loop current and voltage sensing circuit to dynamically determine the signalling state of the far end of the trunk conductors. The microcomputer stores a plurality of data which indicate signalling thresholds for all possible duplex signalling states. The microcomputer can then compare the measured voltage and current on the trunk conductors to automatically make a determination of the signalling state based on the stored data indicative of permissible signalling states.