Coding of sign information in dpcm systems

Claim 2

A digital transmission system comprising: a source of analog signals; means for obtaining regularly recurring differential samples of the analog signals; first means for encoding and transmitting the sign of the differential samples; second means for encoding and transmitting the absolute magnitude of the differential samples; and means for interrupting the transmission of the signals from said second means upon the occurrence of a change in polarity of the differential samples comprising third means for detecting a change in sign of the output of said first means, fourth means for comparing two successively coded output signals of said second means to each other and to a predetermined level when said third means detects a change in sign of the differential sample represented by the second successively coded output signal, and first gating means connected to the output of said first and second means for inhibiting the transmission of the output of said second means and for enabling the transmission of the output of said first means in place of the coded output signal of said second means which is indicative of the smaller of the two successively coded output signals, and said first gating means in response to said fourth means allowing the transmission of the output of said second means for the two successively coded signals upon the occurrence of a change in sign between the two successively coded signals when both exceed the predetermined level.

Claim 3

The digital transmission system of claim 1 wherein means for obtaining regularly recurring differential samples comprises: first decoding means for converting into discrete analog signal levels the output signals of said second means and the output signals of said first means that are transmitted in place of the second of the two successive output signals; second decoding means for converting into discrete analog signal levels the output signals of said second means that are representative of the first successive output signal and are not transmitted; subtracting means for subtracting the output of said second decoding means from the output of said first decoding means; means for producing both a positive and a negative version of the analog signal levels comprising amplifying means connected to the output of said subtracting means; switching means controlled by the said first means for selecting either the positive or the negative signal from said amplifying means; accumulating means for summing the discrete analog signal levels; and subtracting means for obtaining the differential samples by taking the difference between the sampled analog signal and the output of said accumulating means.

Claim 4

The digital transmission system of claim 1 wherein said fourth means comprises means for delaying the output signal of said second means to obtain the two successively coded output signals simultaneously, first comparator means for supplying a signal indicative of the magnitude of the first successive signal when compared to the predetermined level, second compArator means for supplying a signal indicative of the magnitude of the second successive signal when compared to the predetermined level, and third comparator means for supplying a signal indicative of which of the two successive signals is larger by comparing the two successive signals to each other.

Claim 5

The digital transmission system of claim 1 further comprising: fifth means and logic means, both being activated by said first gating means when a change in sign is detected by said third means and the two successively coded output signals exceed the predetermined level of said fourth means, said fifth means supplying an output indicative of the location of the change in sign detected by said third means; second gating means connected to said first and fifth means controlled by said logic means for supplying a polarity signal to accompany the output of said fifth means to indicate the polarity of the output of said second means for the second successive output signal; and said second gating means supplying the run-length and polarity signals to buffering means for storing the signals in said buffer means being transmitted therefrom at a later time between intervals of transmission of the differential samples applied to said first means.

Claim 6

A digital transmission system comprising: a source of digital signals including first and second polarity signals indicative of polarity changes between differential samples, absolute magnitude signals indicative of the absolute magnitude of differential samples, and run-length code signals indicative of the location of polarity changes between differential samples; first gating means for supplying the absolute magnitude signals including substituted polarity signals to delaying means, run-length code signals to first buffering means, and polarity signals associated with the run-length signals to second buffering means; second gating means for combining the run-length coded polarity changes with delayed output signals from said delaying means comprising run-length decoding means connected to said first buffering means, said run-length decoding means controlling said second gating means connected to said delaying means and second buffering means, the output of said delaying means being converted into discrete analog signal levels by said converting means; means for producing both a positive and a negative version of the analog signal levels comprising amplifying means connected to the output of said converting means; said second gating means supplying polarity words to polarity detecting means, said polarity detecting means determining the state of memory means, said memory means maintaining one of two states to indicate the polarity of the absolute magnitude signals; switching means controlled by the state of said memory means for selecting either the positive or negative version of the discrete analog signal levels from said amplifying means; and accumulating means for summing the output of said switching means to construct an analog signal represented by the digital signals.

Claim 7

A digital transmission system comprising: a source of digital signals including first and second polarity signals indicative of polarity changes between differential samples, absolute magnitude signals indicative of the absolute magnitude of differential samples, and run-length code signals indicative of the location of polarity changes between differential samples; first gating means for supplying the absolute magnitude signals including substituted polarity signals to delaying means, run-length code signals to first buffering means, and polarity signals associated with the run-length signals to second buffering means; second gating means for combining the run-length coded polarity changes with delayed output signals from said delaying means comprising run-length decoding means connected to said first buffering means, said run-length decoding means controlling said second gating means connected to said delaying means and second buffering means, the output of said delaying means being converted into discrete analog signal levels by said converting means; means for producing both a positive and a negative version of the analog signal levels comprising amplifying means connected to the output of said converting means; said second gating means supplying polarity words to polarity detecting means, said polarity detecting means determining the state of memory means, said memory means maintaining one of two states to indicate the polarity of the absolute magnitude signals; switching means controlled by the state of said memory means for selecting either the positive or negative version of the discrete analog signal levels from said amplifying means; and accumulating means for summing the output of said switching means to construct an analog signal represented by the digital signals.