Patent GB-1450129-A (GB)
Title: Signal transmission system for transmitting a plurality of informations signals through a plurality of tranmission channels
IPC: H04N7/52
Filed: 1973-08-29
Abstract: 1450129 Television; multiplex technique NIPPON HOSO KYOKAI HITACHI Ltd and HITACHI ELECTRONICS Ltd 29 Aug 1973 [4 Sept 1972 (2)] 40656/73 Headings H4F H4M and H4R  A plurality of information signals a, b, c... z, Fig. 11a, each of arbitrary time period to be transmitted through a plurality of channels in a given time period (e.g. 5 sec.) are arranged in series, Fig. 11b, the resulting signal being split into 5 see. portions, each such portion being transmitted in a separate channel, Fig. 11c, together with signals STX and ETX representing the timings of start and finish of the information signals a, b, ... in the different channels; in addition labels are transmitted with the signals denoting series of one or more information signals together with signals denoting the channels through which these signals are transmitted, a desired series of signals being received by detecting the desired label and hence detecting the channels through which the desired signals are transmitted so that these signals may be reproduced. The system is described as a system wherein the information signals a, b, ... are audio signals accompanying respective video signals each representing a still picture. Output signals occupying 5 sec. are repeatedly transmitted, each period of 5 sec. including 50 video frames and 100 audio frames, one video frame (VF, Fig. 1, not shown) and two audio frames (A 1 F, A 2 F) being transmitted in sequence. Every tenth video frame may be replaced by a code frame (CF). The sound signals shown in Fig. 11c are multiplexed (Fig. 1e, not shown) to provide signals occupying two out of every three television frame periods. The start and end signals STX, ETX are transmitted respectively in the first audio frame (A 1 F) and the second audio frame (A 2 F) of each pair of audio frames. The gap between successive signals shown in Fig. 11b may be restricted to less than <SP>1</SP>/ 10  sec., i.e. each audio signal starts at the beginning of the following series of one video and two audio frames (Fig. 7, not shown) or this gap may be restricted to less than 1 sec., i.e. each signal starts after the following code frame (Fig. 8, not shown). The video and audio signals are derived from recording media 134, Fig. 17, and passed to a transmitter 131. The video signals, each with a video identification code, are fed to a video multiplexing device 169, and the audio signals are passed to a processing device 138 which allocates the signals to different channels under the control of a control device 137. The resulting audio signals are converted at 139 into PCM-TDM (pulse code modulated-time division multiplexed) signals in 144 (96 Î <SP>3</SP>/ 2 ) channels. Transmission codes from 137 are added to the audio signals at 140 and the resulting video and audio signals are passed to a modulator 170 and transmitted to receivers 132, 132<SP>1</SP> ... Each receiver includes a demodulator 171 and a control code decoder 146 which compares transmitted labels with a desired label (indicating desired signals or the address of the receiver) inserted at 147. Identity of these labels opens a video gate 172 for one frame period and feeds the video signal to a buffer memory 173 from which it is repeatedly read out for display. The desired audio signal is extracted by a gate 145 and fed to a D-A converter 148. The labels may be inserted in either the audio or video signals. So that audio signals transmitted in successive channels may be reproduced in sequence from one channel the audio channels may be changed between successive 5 sec. periods, the numbers representing the audio channels in the STX, ETX signals and the signals associated with the labels and representing the audio channels being similarly changed, as are the video identification codes and the signals associated with the labels and representing the video identification codes (Fig. 23, not shown). One video signal may be associated with alternative audio signals (Figs. 24-26, not shown). Either the video signals or audio signals may include spaces or may be omitted entirely.