Asynchronous multiplexing of digitized speech

Claim 2

A variable rate speech multiplexing transmitter in which time slots occurring at a fixed predetermined rate are allocated among a constantly changing number of active speech courses comprising: a plurality of speech sources each presenting an analog speech signal when in an active state, each source including means for shaping the analog original; a plurality of converter means each associated with a particular speech source for converting the analog signal received therefrom to a digitally companded delta sigma modulated signal, each converter means including a companding loop and a tap connected to the loop which presents a full wave rectified signal that follows the average amplitude of the analog speech signal converted therein; a plurality of voice actuated switch means each connected to the tap of one of the converter means to receive a signal therefrom and indicating the active or inactive state of the speech source associated with that converter means, said active or inactive state being determined with reference to a preselected threshold noise level; a plurality of bi-stable storage latch means each connected to a particular voice actuated switch means, the storage latch means being interconnected to form a loop; gating means for periodically supplying timing pulses to the storage latch means and thereby resetting each storage latch means to indicate the active or inactive state of the connected speech source; and register means for combining digitized speech signals received from said converter means to form a data stream including digitized time division signals from only those converter means associated with speech sources that the storage latch means indicates are active, the register means thus providing an output in which the rate at which any active speech source is sampled varies and is dependent upon the number of other simultaneously active speech sources in the system.

Claim 3

The apparatus of claim 1 further comprising synchronizing means responsive to the storage latch means for generating channel identifying information identifying time slots corresponding to particular speech sources and for supplying current channel identifying information to said register means at fixed and predetermined intervals.

Claim 4

The apparatus of claim 2, wherein said synchronizing means generates identifying information that identifies time slots associated with particular channels without reference to previously generated identifying information.

Claim 5

A variable rate speech multiplexing transmitter in which time slots occurring at a fixed prEdetermined rate are allocated among a constantly changing number of active speech sources comprising: a plurality of speech sources each presenting an analog speech signal when in an active state, each speech source including means for shaping the analog signal and means for preemphasizing the analog signal; a plurality of converter means each associated with a particular speech source for converting the analog signal from that source to a digitized speech signal; a plurality of voice actuated switch means each associated with a particular speech source for indicating the active or inactive state thereof determined with reference to a preselected threshold noise level; a plurality of bi-stable storage latch means each connected to a particular voice actuated switch means, the storage latch means being interconnected to form a loop; gating means for periodically supplying timing pulses to the storage latch means and thereby resetting each storage latch means to indicate the active or inactive state of the connected speech source; synchronizing means responsive to said storage latch means for generating channel identifying information identifying time slots corresponding to particular speech sources without reference to previously transmitted identifying information and for supplying said channel identifying information to the register means at fixed and predetermined intervals; and register means for combining digitized speech signals received from the converter means to form a data stream including digitized time division signals from only those converter means associated with speech sources that the storage latch means indicates are active and for interleaving with said digitized speech signals at fixed and predetermined intervals the identifying information received from the synchronizing means, thereby providing an output wherein the rate at which any active speech source is sampled varies and is dependent upon the number of other simultaneously active speech sources in the system.

Claim 6

A variable rate speech multiplexing transmitter in which time slots occurring at a fixed prEdetermined rate are allocated among a constantly changing number of active speech sources comprising: a plurality of speech sources each presenting an analog speech signal when in an active state, each speech source including means for shaping the analog signal and means for preemphasizing the analog signal; a plurality of converter means each associated with a particular speech source for converting the analog signal from that source to a digitized speech signal; a plurality of voice actuated switch means each associated with a particular speech source for indicating the active or inactive state thereof determined with reference to a preselected threshold noise level; a plurality of bi-stable storage latch means each connected to a particular voice actuated switch means, the storage latch means being interconnected to form a loop; gating means for periodically supplying timing pulses to the storage latch means and thereby resetting each storage latch means to indicate the active or inactive state of the connected speech source; synchronizing means responsive to said storage latch means for generating channel identifying information identifying time slots corresponding to particular speech sources without reference to previously transmitted identifying information and for supplying said channel identifying information to the register means at fixed and predetermined intervals; and register means for combining digitized speech signals received from the converter means to form a data stream including digitized time division signals from only those converter means associated with speech sources that the storage latch means indicates are active and for interleaving with said digitized speech signals at fixed and predetermined intervals the identifying information received from the synchronizing means, thereby providing an output wherein the rate at which any active speech source is sampled varies and is dependent upon the number of other simultaneously active speech sources in the system.