Method and apparatus for telephone line multiplex channeling of toll-quality voice and digital information
AssigneeAcademy of Applied Science
InventorRichard D. Greenblatt
Life of this patent
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Abstract
A method and apparatus for telephone line multiplex channeling of toll-quality voice and modem-encoded digital data from telecommunication devices (FAX, computers, displays, printers, etc.) involving variably sample-compression of digitally converted voice signals within successive time frames, and filling the resulting unoccupied time within each such frame with the modem-encoded digital data, and preferably with guard band signals separating the voice and modem-encoded digital data within each frame.
Claims16
A method of multiplexing voice-produced audio signals and modem-encoded digital data from telecommunications devices to achieve "data-under-voice" telephone communication while retaining toll-quality voice, comprising converting the audio signals into digital form and then sampling the digitized audio signals at a predetermined rate within a selected time frame of a plurality of equal time frames and storing in buffer means;
- playing back from the buffer means the sampled digitized audio signals during the next successive time frame in a shorter time than the sampling during the preceding time frame by effectively increasing the rate of sampling per unit time, thereby leaving an unoccupied time interval for the remainder of the frame;
- and inverting the modem-encoded digital data into the unoccupied time interval created by the increasing of the rate of sampling during the playing back.
Apparatus for telephonically over a telephone channel transmitting and receiving between transmitting and receiving telephones voice-produced audio signals and modem-encoded digital data from telecommunications devices while retaining toll-quality telephone voice having, in combination, means for generating a plurality of equal time frames for signal transmission and reception;
- encoding voice channel means comprising a first pair of alternately filling and emptying buffers connected in multiplexing fashion to an a first analog-to-digital converter receiving analog audio signals and clocked at a predetermined sampling rate;
- a first digital-to-analog converter clocked at a higher rate and connected to the first pair of buffers for restoring and playing back the analog audio signals at the output;
- multiplexing controlling means comprising means for sampling the digitally converted audio signals at the predetermined rate during one frame and to play back the sampled digitized audio signals from the first pair of buffers at said higher rate achieving compression during the next frame, leaving an unoccupied time interval for the remainder of said next frame;
- and means for inserting the modem-encoded digital data into the unoccupied time interval for transmission along the telephone channel with the audio signals.
Dependencies are inferred from the claim text.