At&t Bell Laboratories

Joseph G Klinger

Raymond W Bennett

Rafid Antoon Sukkar

Brian C Prorok

A method and apparatus for detecting dual-tone, multi-frequency (DTMF) digits and call progress tones by determining the amplitudes of preselected frequencies in a signal over a predetermined time period, and determining a candidate tone by selecting two of the preselected frequencies with the highest amplitudes and comparing the two selected frequencies to known DTMF and call progress tone frequencies. The amplitudes of the two selected frequencies are then tested against predefined thresholds corresponding to a candidate tone having the two selected frequencies. The candidate tone in the current time period is tested against candidate tones in previous time periods for consistency. If the candidate tone is a DTMF digit and passed all of the tests, then the DTMF digit is returned. If the candidate tone is a call progress tone, the pattern of the candidate tone over a plurality of predetermined time periods is recorded and tested against known patterns of the candidate tone. If the candidate tone meets all of the above tests, the call progress tone is returned.

Apparatus and method for audible signaling tone recognition

An arrangement providing a monitor-on-hold feature for telephone station apparatus. The exemplary apparatus includes a handset transmitter and receiver, a speaker, and four user control buttons. A user is given the capability to move a connection for a first call from the handset to the speaker by simply actuating one of the buttons, the PRIVACY button. A connection is thereafter completed to the handset to answer a second call in privacy by actuating a second button, the NEWCALL button, while continuing to monitor the first call via the speaker. The capability to move connections is provided by a microprocessor-controlled switch included within the apparatus to selectively interconnect the two communications channels used for the two calls, with the handset and the speaker. Alternatively, the moving of connections is effected within the switching system serving the telephone station.

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Waterman, IL, United States of America

Joseph G Klinger