Band-energy near-end echo reducer for tonal signalling detectors

Method of minimizing an echo component from a remote signal, comprising:

• passing transmit signals from a phone system through a system hybrid to a phone line;
• passing remote signals from the phone line, said remote signals including a near-end echo of the transmit signals;
• filtering and squaring the transmit signals;
• filtering and squaring the remote signals;
• multiplying the filtered/squared transmit signals by a a compensator gain coefficient and producing a resultant signal;
• and
• subtracting the resultant signal from the filtered/squared remote signals to produce an echo-cancelled receive signal.

A multi-tone decoder system comprising:

• a plurality of tone detectors, each tone detector including:
• a transmit filter function and a receive filter function,
• a multiplier multiplying an output of the transmit filter function by a coefficient, said coefficient selected such that a given transmit filter detects a pre-defined frequency of interest,
• an adder subtracting an output of the receive filter function from an output of the multiplier and providing a tone detection output indicative of a pre-defined tone at the pre-defined frequency of interest;
• and
• tone detection logic receiving the plurality of tone detection outputs and comparing the tone detection outputs against a detection threshold for each tone detection output to determine presence or absence of a pre-defined tone on each tone detection output.