GB584457A - Synchronising circuit for multiplex electric impulse communication systems - Google Patents

Abstract

584,457. Multiplex signalling. STANDARD TELEPHONES & CABLES, Ltd. Aug. 1, 1944, No. 14674. Convention date, Sept. 29, 1943. [Class 40 (v)] In a multiplex time-modulation pulse signalling system, in which a plurality of time modulated trains of signal impulses are combined in time displaced relation, the receivers are synchronised by means of impulses derived from a resonant circuit tuned to the mean combined pulse repetition frequency of the composite signal train. One of the trains of impulses may be utilised as a monitor channel, means being provided at the receiver station to observe the monitoring interval and align the receivers with their proper channels. The pulse transmitters 1, 2, 3, for the signal channels 21, &c., are operated in sequence by means of impulses derived from the source 10 over phaseshifters 11, &c. The additional transmitter M derives a monitoring signal from the source 24 and is operated in sequence with the transmitters 1, &c., over the additional phaseshifter 13. The combined impulses are applied to the line 70, and at the receiving station are applied to the receivers 31 &c., and 3M and the synchronising source 29. The synchroniser 29 may comprise a circuit 27 tuned to the mean combined pulse petition frequency, or may be an oscillator held in synchronism by the pulses. The output is applied to a frequency divider 25, producing impulses which are applied over the adjustable phase-shifter 26 and individual phase-shifters 34, &c., to operate in proper sequence the receivers 31 &c., and 3M, correct channel alignment being achieved by adjustment of the phase-shifter 34 until the monitoring signal is received in the channel 3M. The receivers 31, &c., may be of the type described in Specification 600,291. In an arrangement of this type the demodulating wave may be derived from a frequency converter 125 operating from the synchroniser 29, and may be applied to the receivers 31, &c., over an adjustable phaseshifter 130 and the individual phase-shifters 131, &c. Return channel. The pulse transmitters 41, &c., for the return channels 51, &c., derive operating impulses from the frequency divider 25, over phase-shifters . 44, &c., the return monitoring channel comprising the transmitter 4M and monitoring source 54. The receivers 61 &c. and the monitoring receiver 6M, are synchronised from the source 10 over the adjustable phase-shifter 67 and individual phase-shifters 64, &c. They derive demodulating waves from the frequency multiplier 150 controlled by the source 10, over adjustable phase-shifter 160 and individual phase-shifters 161, &c. In an alternative arrangement (Fig. 3, not shown), the transmitters 1, &c., derive energy directly from the control wave source 10, the modulated pulses of the separate channels then being suitably spaced by individual delay lines to permit of combination to a multiplex wave. Specifications 509,820 and 600,244 also are referred to.