GB873934A - Improvements relating to multiplex transmission systems - Google Patents

Abstract

873,934. Multiplex pulse signalling. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Aug. 11, 1959 [Aug. 11, 1958], No. 25744/58. Class 40(5) A multiplex transmission system includes at the transmitter a storage device into which the multiplexed signal samples are written in recurrent parallel sweeps (e.g. columns) to form a rectangular matrix, Fig. 1, in which signal samples of the respective channels are aligned laterally (i.e. in rows), the signal samples being read out in recurrent lateral sweeps (rows) so that bursts of signals from each channel are transmitted in turn, and means are provided to prevent a read-out sweep taking place on a line in which no signal samples were stored in the preceding writing frame. Preferably, two storage devices are employed signals being written into one device while signals of the preceding frame are being read out of the other device. A similar storage device or a pair of devices is employed at the receiver, lines having no signals being omitted during writing, but included during reading whereby the original multiplexed train is obtained for distribution to the respective channel receivers. A line synchronizing pulse is transmitted at the end of each line read out, two line synchronizing pulses following each other in close succession when a line is omitted, and the frame scan generators at the transmitter and receiver being stepped to the next line each time a line synchronizing pulse occurs. Long frame synchronizing pulses are transmitted at the end of each read-out frame to reset the frame scan generators. Alternatively a coded group of pulses may be employed to provide frame synchronization. The read-out line scanning speed at the transmitter is preferably greater than the writing line scanning speed whereby pulse frequency compression is obtained, corresponding expansion taking place at the receiver.