# US 5,353,168 A · Recording and reproducing system using time division multiplexing

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- Number: US 5,353,168 A
- Document ID: US5353168A
- Status: Granted
- Kind: A
- Application number: 07/972,080
- Filed: 1992-11-05
- Granted: 1994-10-04
- Earliest claimed: 1990-01-03
- Assignees: Racal Recorders Limited
- Inventors: Neil M. Crick
- Web page: https://patentgrep.com/patent/US5353168A

## CPC

- G11B 20/00: Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B 5/0086: {using cyclically driven heads providing segmented tracks}
- G11B 20/1207: {with transverse tracks only}
- G11B 2020/10546: {specifically adapted for audio data}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

A system for recording analogue and/or digital signals (especially analogue voice signals) on magnetic tape has a plurality of individual input channels and a time division multiplexing circuit which samples the analogue signals in the input channels cyclically, in a pre-arranged sequence. The samples are output to a single output channel for recording on a standard VHS magnetic tape. In the replay mode, recorded signals are distributed to respective output channels by a demultiplexing circuit.

## Claims

### Claim 1

A recording and reproducing system comprising,
a plurality of individual input channels for receiving respective input signals having respective levels;
time division multiplexing means for sampling the respective input signals cyclically, according to a predetermined sequence of the input channels and for outputting a succession of samples occupying respective time slots, each sample representing a level of an input signal received in a respective input channel during a respective time slot, the samples derived from one of the input channels being used as synchronisation signals;
frequency modulation means for frequency modulating the succession of samples output by said time division multiplexing means to produce frequency-modulated samples;
means for recording the frequency-modulated samples, as an analogue signal, on magnetic recording tape;
means for reading the frequency-modulated samples from the magnetic recording tape;
frequency demodulation means for demodulating the frequency modulated samples read by the reading means to produce a succession of frequency-demodulated samples,
a plurality of output channels, each output channel corresponding to a respective input channel;
time division demultiplexing means for distributing the frequency-demodulated samples output by said frequency-demodulation means to respective output channels; and
synchronisation signal detection means for detecting the frequency-demodulated samples that are used as synchronisation signals, the time division demultiplexing distributing the frequency-demodulated samples output by said frequency demodulation means to respective output channels in accordance with the timing of the detected synchronisation signals.

### Claim 2 (depends on 1)

A recording and reproducing system as claimed in claim 1, wherein at least some of the input channels include a low pass filter responsive to frequencies in a range from 300 Hz to 3.4 kHz.

### Claim 3 (depends on 2)

A recording and reproducing system as claimed in claim 2, wherein said time division multiplexing means has a sampling cycle of predetermined period, and the time division multiplexing means samples the input signals received in physically neighbouring said input channels at respective times during each sampling cycle that are separated in time by half said predetermined period.