Delta modulation communication system

Claim 2

A delta modulation system for providing successive digital words to represent the information contained in successive groups of digital elements, the digital words to have generally fewer numbers of digital elements than the successive groups of digital elements, said system comprising: means responsive to said successive groups of digital elements for determining when the difference between adjacent groups of digital elements is within a predetermined range; means for encoding said successive groups of digital elements and operative in response to a determination that said difference is within said predetermined range to provide a digital word corresponding to said difference; said encoding means including means operative in the absence of said determination for providing a digital word corresponding to a group of digital elements itself.

Claim 3

A delta modulation system as set forth in claim 1 including means for adding a digital flag signal to the succession of digital words preceding each digital word corresponding to a group itself.

Claim 4

A delta modulation system for providing successive digital words to represent successive groups of digital elements wherein each group represents a numerical value, said system comprising: means responsive to said successive groups of digital elements for determining whether the values represented by adjacent ones of said groups differ numerically by more than a predetermined numerical value; and means for encoding said groups of digital elements and operative in response to a value difference determined not to be more than said predetermined value to provide a digital word corresponding to said value difference according to a first coding scheme; said encoding means further including means operative in response to a value difference determined to be more than said predetermined value for providing a digital word approximating the absolute value of a group of digital elements according to a second coding scheme.

Claim 5

A delta modulation system for providing successive digital words to represent successive groups of digital elements wherein each group represents a numerical value, said system comprising: means responsive to said successive groups of digital elements for determining whether the values represented by adjacent ones of said groups differ numerically by more than a predetermined numerical value; and means for encoding said groups of digital elements and operative in response to a value difference determined not to be more than said predetermined value to provide a digital word corresponding to said value difference according to a first coding scheme; said encoding means further including means operative in response to a value difference determined to be more than said predetermined value for providing a digital word approximating the absolute value of a group of digital elements according to a second coding scheme.

Claim 6

The delta modulation system of claim 3: wherein said encodiNg means includes means for providing a digital indication in the succession of digital words of the coding scheme used; and further including as means for recovering a sequence of groups of digital elements from the digital words: means for decoding said digital words and responsive to a digital indication of use of said first coding scheme to provide a group of digital elements differing in value from the preceding group in the recovered sequence by the value difference corresponding to that digital word; said decoding means having means responding to an indication of use of said second coding scheme to provide groups of digital elements having values corresponding to the values represented by said digital words.

Claim 7

The delta modulation system of claim 3 wherein the digital words of said first and second coding schemes contain substantially fewer numbers of digital elements than in said groups of digital elements whereby digital words from said first coding scheme are capable of representing a limited range of value differences substantially smaller than the range of values representable by said groups of digital elements and further whereby the digital words of said second coding scheme are generally capable of representing an approximation to the absolute values of said groups of digital elements within a predetermined error.

Claim 8

The delta modulation system of claim 5 further including means for relfecting the error in the approximation of a digital word from said second coding scheme into subsequent digital words thereby to reduce the propagation of the error in the digital words from said second coding scheme.

Claim 9

A delta moduation system for providing a succession of code words corresponding to digital samples of an analog signal including: means for repetitively sampling said analog signal; means for providing a multi-bit digital word of each sample using digital words selected from a first vocabulary capable of representing a first plurality of values of said analog signal; repeated sampling of said analog signal resulting in a sequence of digital words; means for examining said sequence and operative to provide simultaneous examination of adjacent digital words; means for providing an output indication when examined adjacent digital words in said sequence differ in value by more than a predetermined value; first means operative in the absence of said output indication for generating a digital code selected from a second vocabulary to represent the difference in value between the corresponding adjacent digital words, said second vocabulary having substantially fewer digital codes than said first vocabulary; and second means responsive to said output indication for generating a digital code from a third vocabulary to approximate one of said examined adjacent digital words, said third vocabulary having words representative of a limited number of values distributed over the range of said analog signal.

Claim 10

A delta moduation system for providing a succession of code words corresponding to digital samples of an analog signal including: means for repetitively sampling said analog signal; means for providing a multi-bit digital word of each sample using digital words selected from a first vocabulary capable of representing a first plurality of values of said analog signal; repeated sampling of said analog signal resulting in a sequence of digital words; means for examining said sequence and operative to provide simultaneous examination of adjacent digital words; means for providing an output indication when examined adjacent digital words in said sequence differ in value by more than a predetermined value; first means operative in the absence of said output indication for generating a digital code selected from a second vocabulary to represent the difference in value between the corresponding adjacent digital words, said second vocabulary having substantially fewer digital codes than said first vocabulary; and second means responsive to said output indication for generating a digital code from a third vocabulary to approximate one of said examined adjacent digital words, said third vocabulary having words representative of a limited number of values distributed over the range of said analog signal.

Claim 11

The delta modulation system for digitally describing an analog signal of claim 7 and further including: means operative in association with said second generating means for providing in a subsequent one of said digital codes a component reflecting the error in the approximation from said third vocabulary.

Claim 12

The delta modulation system of claim 8 further including: means for receiving the digital codes from said first and second generating means; means operative in response to received digital codes from said first generating means to provide words from said first vocabulary with sequentially differing digital values representative of the received digital codes from said first generating means; and means operative in response to received digital codes from said second generating means to provide corresponding digital words from said third vocabulary; means for causing digital words provided subsequent to those in response to the digital codes from said second generating means to be provided to reduce the error reflected in digital codes from said second generating means thereby to refine the approximation and reduce the error in successive digital words.

Claim 13

A delta modulation system for providing a sequence of digital codes to describe an analog signal and including: means for repetitively sampling said analog signal; means for providing a multi-bit digital word for each sample with a digital word from a vocabulary of words for describing a plurality of discrete values of said analog signal, the repetitive sampling resulting in a sequence of said digital words; means for providing coincident temporary storage of adjacent digital words in said sequence; means for providing a digital difference output to represent the difference in value between the stored adjacent words; means for providing an output indication whenever the digital difference output exceeds a predetermined value; means operative in response to said output indication for selecting a digital code comprising the most significant bits of one of said stored digital words; means further operative in response to said output indication for generating a digital code to indicate a predetermined change in value for said analog signal less than the smallest value difference representable by said most significant bits; and means operative in response to the absence of said output indication for selecting said digital difference output as the digital code for one of said stored digital words.

Claim 14

A delta modulation system for providing a sequence of digital codes to describe an analog signal and including: means for repetitively sampling said analog signal; means for providing a multi-bit digital word for each sample with a digital word from a vocabulary of words for describing a plurality of discrete values of said analog signal, the repetitive sampling resulting in a sequence of said digital words; means for providing coincident temporary storage of adjacent digital words in said sequence; means for providing a digital difference output to represent the difference in value between the stored adjacent words; means for providing an output indication whenever the digital difference output exceeds a predetermined value; means operative in response to said output indication for selecting a digital code comprising the most significant bits of one of said stored digital words; means further operative in response to said output indication for generating a digital code to indicate a predetermined change in value for said analog signal less than the smallest value difference representable by said most significant bits; and means operative in response to the absence of said output indication for selecting said digital difference output as the digital code for one of said stored digital words.

Claim 15

The delta modulation system of claim 10 wherein: said digital difference output selecting means is operative to provide digital codes from a vocabulary having fewer digital codes than the number of possible multi-bit digital words for the analog signal samples; and said system further including means for encoding the digital words for said digital difference output in a first digital code from said vocabulary and a correction applied in a subsequent digital code.

Claim 16

A delta modulation system for digitally describing an analog signal including, in combination: sampling means for taking successive analog signal samples and for converting each sample of the analog signal into a sequence of words of six digital bits representing the sample value; differencing means for producing a digital word representing the difference in value between each current sample of the analog signal and the preceding sample; decision means for determining if the value of the digital word representing said difference is greater than a predetermined value; said decision means producing a first output signal if the difference is no greater than the predetermined value and a second output signal if the difference is greater than the predetermined value; means for transmitting a digital word comprising the three lowest order bits of the digital word representing said difference in response to the first output signal; and means for transmitting a digital word comprising the three highest order bits of a sample word in response to the second output signal.

Claim 17

A delta modulation system for digitally describing an analog signal including, in combination: sampling means for taking successive analog signal samples and for converting each sample of the analog signal into a sequence of words of six digital bits representing the sample value; differencing means for producing a digital word representing the difference in value between each current sample of the analog signal and the preceding sample; decision means for determining if the value of the digital word representing said difference is greater than a predetermined value; said decision means producing a first output signal if the difference is no greater than the predetermined value and a second output signal if the difference is greater than the predetermined value; means for transmitting a digital word comprising the three lowest order bits of the digital word representing said difference in response to the first output signal; and means for transmitting a digital word comprising the three highest order bits of a sample word in response to the second output signal.

Claim 18

A delta modulation system for digitally describing an analog signal including, in combination: sampling means for repetitively sampling the value of the analog signal; quantizing means for converting each sample of the analog signal into a sequence of digital words each including a given number of digital bits; differencing means for producing a digital word representing the difference in value between each current sample of the analog signal and the preceding sample; decision means for determining if the value of the digital difference is greater than a predetermined value; a digital word vocabulary for the digital word representing said difference having digital words of fewer bits than said given number of digital bits; said decision means producing a first signal if the digital difference is no greater than the predetermined value and a second signal If the difference is greater than the predetermined value; means for transmitting a digital code word from a vocabulary having code words of the same number of digital bits as said difference representing digital word to describe the difference between the current and preceding sample values in response to the first signal; and means operative in response to said second signal for transmitting a flag digital code word of said same number of bits followed by a digital code word of said number of bits corresponding to the sample value itself; said transmitting means being operative to transmit a first specific one of the code words in said vocabulary when the current and previous sample values are the same; said transmitting means further being operative to approximate the difference in sample value which equals said predetermined value and to modify the succeeding digital code word to cause it to represent the difference between the approximation and the next sample value.

Claim 19

A delta modulation system for digitally describing an analog signal including, in combination: sampling means for repetitively sampling the value of the analog signal; quantizing means for converting each sample of the analog signal into a sequence of digital words each including a given number of digital bits; differencing means for producing a digital word representing the difference in value between each current sample of the analog signal and the preceding sample; decision means for determining if the value of the digital difference is greater than a predetermined value; a digital word vocabulary for the digital word representing said difference having digital words of fewer bits than said given number of digital bits; said decision means producing a first signal if the digital difference is no greater than the predetermined value and a second signal If the difference is greater than the predetermined value; means for transmitting a digital code word from a vocabulary having code words of the same number of digital bits as said difference representing digital word to describe the difference between the current and preceding sample values in response to the first signal; and means operative in response to said second signal for transmitting a flag digital code word of said same number of bits followed by a digital code word of said number of bits corresponding to the sample value itself; said transmitting means being operative to transmit a first specific one of the code words in said vocabulary when the current and previous sample values are the same; said transmitting means further being operative to approximate the difference in sample value which equals said predetermined value and to modify the succeeding digital code word to cause it to represent the difference between the approximation and the next sample value.

Claim 20

A delta modulation system as set forth in claim 13 including, in combination, means for receiving said transmitted digital code words; means for integrating the sample value difference represented by each successive received digital code word representing a value difference with previous sample value differences to produce an output representative of the successive sample values of the original analog signal; means for resetting the integrating means to the sample value represented by each digital code word representing a sample value itself; means for producing a flagging signal in response to each flag digital code word in the received code word sequence; and means for causing the integrating means to integrate each successive sample value difference and for causing resetting of the integrating means in response to the flag signal to the same value represented by the digital code word following the flag code word in the received succession.

Claim 21

A delta modulation system as set forth in claim 14 in which: the digital code words which represent the difference between sample values represent substantially all of the possible sample value differences between reference sample values defined as values corresponding to code words which represent the sample itself; and the means for resetting the integrating means in response to the flag code word resets the integrating means to the reference sample value identified by the digital code word following the flag code word.