Limiting maximum gain in duplex communications devices including telephone sets

Abstract

Duplex communication methods and systems with maximum gain limiting such as in telephone handsets and speaker phones are disclosed. The communications system such as a telephone set may generally include a digital signal processor (DSP) having a receive and transmit path in communication with a receiver and a transmitter, respectively, a volume amplifier for amplifying signals on the receive path, and a maximum gain limiter for determining a total return loss between the receive and transmit paths and for limiting a volume amplification level of the volume amplifier to a maximum depending on the total return loss. The maximum gain limiter determines the total return loss by maintaining a total loop gain for the telephone set at less than 0 dB to prevent unstable operation and howling.