# US 4,393,371 A · Analogue to digital signal conversion and storage system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,393,371 A - Document ID: US4393371A - Status: Granted - Kind: A - Application number: 06/264,232 - Filed: 1981-05-18 - Granted: 1983-07-12 - Earliest claimed: 1979-06-05 - Assignees: Morgan-Smith Electronics Ltd. - Inventors: Peter J. Morgan-Smith - Web page: https://patentgrep.com/patent/US4393371A ## CPC - H03M 1/127: {at intervals varying with the rate of change of the input signal} - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) ## Abstract In an analogue to digital converter, the analogue signal applied thereto is sampled at successive time intervals and at each sample a digital signal is produced and the time interval between successive samples is not necessarily constant but is dependent upon the rate of change of amplitude of the analogue signal during said time interval. The digital signals may be applied to a counter to produce data representative of the time interval between successive samples and also to indicate whether the analogue signal has increased or decreased between successive samples. This data may then be recorded in a manner to provide substantially constant recording density. ## Claims ### Claim 1 An analogue-to-digital signal conversion and storage system including means for sampling the analogue signal at successive time intervals and producing at each sample a digital signal, the interval between successive samples being dependent upon the rate of change of amplitude of the analogue signal during said time interval, timing means for determining the time interval between successive samples, storage means including a data buffer to which data from the system is supplied and from which data is applied to a recording means, the speed at which data is stored in the recording means being variable, and means for producing a control signal for adjusting said speed in response to the amount of data stored in the buffer, said signal being arranged to prevent overload of the buffer. ### Claim 2 (depends on 1) An analogue-to-digital signal conversion and storage system as claimed in claim 1, in which the analogue signal is sampled when the instantaneous amplitude of the signal changes by a predetermined amount from the instantaneous amplitude of the signal at the previous sample. ### Claim 3 (depends on 1) An analogue-to-digital data conversion and storage system as claimed in claim 1, including means for converting said stored data to an analogue signal. ### Claim 4 (depends on 1) An analogue-to-digital signal conversion and storage system as claimed in claim 1, in which the storage means includes means for scanning the storage medium at a variable speed related to the frequency content of the analogue signal. ### Claim 5 (depends on 2) An analogue-to-digital signal conversion and storage system as claimed in claim 2, in which the predetermined change in amplitude is variable. ### Claim 6 (depends on 3) An analogue-to-digital signal conversion and signal system as claimed in claim 3, in which the means for converting said storage data to an analogue signal includes a current generator whose output current is determined by the data input thereto and a capacitor arranged to receive the output of said generator. ### Claim 7 (depends on 1, 2, 5) An analogue-to-digital conversion and storage system as claimed in claims 1, 2 or 5, further comprising a sample-and-hold circuit having an input for receiving the analogue signal, means for applying positive and negative offset signals to the analogue signal and means for comparing the output of the sample-and-hold circuit with the output of said offset means for producing a first digital signal when the output of the sample-and-hold circuit and that of the offset means bear a predetermined relationship and a second digital signal representative of the polarity of the change in instantaneous amplitude of the analogue signal since the preceeding sample. ### Claim 8 (depends on 1, 2, 5) An analogue-to-digital signal conversion and storage system as claimed in claims 1, 2 or 5 further comprising a sample-and-hold circuit having an input for receiving the analogue signal, means for applying positive and negative offset signals to the output of the sample-and-hold circuit and means for comparing the analogue signal with the output of said offset means and for producing a first digital signal when the analogue signal and the output of the offset means bear a predetermined relationship and a second digital signal representative of the polarity of the change in instantaneous amplitude of the analogue signal since the preceeding sample. ### Claim 9 (depends on 7) An analogue-to-digital converter as claimed in claim 7, including a counter to which the first digital signals are applied, the counter producing data representing the time between successive samples. ### Claim 10 (depends on 8) An analogue-to-digital converter as claimed in claim 8, including a counter to which the first digital signals are applied, the counter producing data representing the time between successive samples. ### Claim 11 (depends on 9) An analogue-to-digital signal conversion and storage system as claimed in claim 9, including a semiconductor memory in which both the output data from the counter and data representative of the second digital signals is stored.