Multiplex conference bridge
AssigneeE-Systems, Inc.
InventorsWilliam L. Betts, L. Ray Blackman
Life of this patent
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Abstract
A conferencing circuit for use in a digitized voice, time division multiplex (TDM) loop communication system. Digitized speech samples from conferee subscriber stations are extracted from the TDM loop and summed over a frame interval. The sum is stored and the input from each subscriber station is subtracted from the sum and the remainder is placed on the TDM loop for return to the respective station. A conference control signal is generated which is synchronous with the TDM loop and the subscriber station's time slot and has a given state for each slot assigned to a subscriber station that participates in the conference. The conference control signal controls the circuitry which sums the digitized speech samples generated by the conference subscriber stations.
Claims5
Apparatus for establishing a conference call between a plurality of subscriber stations on a time division multiplex loop wherein each subscriber station is assigned a time slot within a frame for transmitting and receiving digitized speech samples, comprising:
- (a) means for generating a control signal synchronous with said frame and having a first state in time coincidence with each time slot which is assigned to a subscriber station in the conference call and a second state in time coincidence with each time slot which is assigned to a subscriber station not included in the conference call,
- (b) an accumulating register for accumulating therein a sum of digitized speech samples generated by the conference subscriber stations, said accumulating register operating responsively to said control signal to receive inputs and transfer the contents thereof as an output,
- (c) means for adding digitized speech samples received from said conference subscriber stations through said multiplex loop to the output from said accumulating register and for transferring the output of said means for adding to said accumulating register,
- (d) a storage register having the input thereof connected to receive said sum from said accumulating register at the end of each frame,
- (e) delay means connected to said multiplex loop for delaying for approximately one frame period the digitized speech samples generated by said subscriber stations,
- (f) subtracting means connected to receive said sum from said storage register and the output of said delay means for sequentially subtracting each of the delayed digitized speech samples from the sum received from said storage means to produce a series of partial sums, and
- (g) means for transferring said partial sums in synchronism with said control signal from said subtracting means through said multiplex loop to said conference subscriber stations, each conference subscriber station receiving the partial sum comprising the summation of the digitized speech samples generated over one frame by the remaining subscriber stations in the conference call.
A method for establishing a conference call between a plurality of subscriber stations on a time division multiplex loop wherein each subscriber station is assigned a time slot within a frame for transmitting and receiving digitized speech samples, comprising the steps of:
- (a) generating a control signal which is synchronous with said frame and has a first state in time coincidence with each time slot which is assigned to a subscriber station in the conference call and a second state in time coincidence with each time slot which is assigned to a subscriber station not included in the conference call,
- (b) accumulating in an accumulating register a sum of the digitized speech samples generated by the conference subscriber stations over one frame, said accumulating register receiving inputs and transferring the sum as an output in response to said control signal,
- (c) adding in an adding means the digitized speech samples received from said conference subscriber stations through said multiplex loop to the output from said accumulating register and transferring the output of the adding means to said accumulating register,
- (d) storing in a storage register at the end of each frame the sum accumulated in said accumulating register over one frame,
- (e) delaying for approximately the period of one frame the digitized speech samples received through said multiplex loop from said conference subscriber stations,
- (f) sequentially subtracting in a subtracting means each of the delayed digitized speech samples from the sum stored in said storage means to produce a series of partial sums, and
- (g) transferring said partial sums in synchronism with said control signal through said multiplex loop to said conference subscriber stations, each subscriber station receiving the partial sum comprising the summation of the digitized speech samples generated over one frame by the remaining subscriber stations in the conference call.
Dependencies are inferred from the claim text.