Abstract: In the transmitter portion a multiplexer multiplexes first digital data and first teletype signals to provide first digital data signals. The first digital data signals are converted into second digital data signals having a different form than the first digital data signals by a Viterbi coder. A PSK modulator responsive to the second digital data signals provides a first PSK signal for transmission. In the receiver portion a PSK demodulator receives a second PSK signal containing third digital data signals having multiplexed second digital data and second teletype signals with the third digital data signals being extracted from the second PSK signal. A Viterbi decoder converts the third digital data signals into fourth digital data signlas having a different digital form than the third digital data signals. A PSK demultiplexer is responsive to the fourth digital data signals to separate the second digital data and the second teletype signals for utilization.

Abstract: This invention relates to a digital vocoder where speech is translated to a digital version thereof. An adaptive filter in the form of an N stage Itakura type cascade derives from the speech a prediction residual and N spectral parameter in the form of weighting coefficients of the filter. The pitch period, derived from the prediction residual, the voiced/unvoiced decision derived from the first of the weighting coefficients and the peak amplitude of a pitch pulse, and a digital signal representing filter gain, derived from the last of the weighting coefficients are multiplexed with each other and the N spectral parameters for transmission to a receiver. The receiver employs an excitation generator responsive to the pitch period, the gain signal and the voiced/unvoiced decision to produce an excitation signal to excite an N/2 cascade connected stage receive filter. Each stage of the receive filter operates on a time shared basis on an adjacent pair of the N spectral parameters.

Abstract: There is disclosed a digital conference bridge for a delta modulated switching system having information transmitted by delta modulation bits in M channels of a time division multiplex frame, where M is an integer greater than three. N conferees, where N is an integer greater than two but less than M, are interconnected by a time switch to enable a conference to take place among the conferees. N three stage shift registers are provided, one for the delta modulation bits of each of the conferees. N sequence detectors are coupled to an associated one of the shift registers to produce a binary 1 output when bits stored in the shift register are all binary 1 or all binary 0. N counters each have their count increased by the binary 1 output of an associated one of the sequence detectors. A count comparator is coupled in common to all the counters and produces a control signal indicating a new speaker for the counter having the largest count.