GB1069955A - Improvements in or relating to data signal transmission systems - Google Patents

Abstract

1,069,955. Data transmission ; multiplex signalling. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. Aug. 4, 1964 [July 23, 1963], No. 30623/64. Headings H4L and H4P. Phase-modulated data is amplitude-modulated to provide a synchronizing signal at the receiver in a data transmission system. The system described has two binary data inputs at A, B which feed relays R A , R B . Unit T produces clock pulses at bit frequency, adjacent pulses having different amplitudes, as indicated. The clock pulses pass to contacts r A , r B both direct and via inverter U. The resultant pulse trains indicate the sign of the bit by their polarity, adjacent pulses having different amplitudes. After filtering at F A , F B and modulating at M A , M B with quadrature carriers, the signals are combined at S to give a phasemodulated data signal in which the phase rela. tive to that during the previous, clock period determines'the combination of bits on the input channels and in which the amplitude provides a sync. signal. At the receiver the phase-modulated signals are detected as indicated, and the amplitude modulation, by' way of rectifier G, excites a ringing circuit which feeds frequency doubler FV. The output of this unit is shaped at JF to provide clock pulses which operate. switches AS A <SP>1</SP>, AS B <SP>1</SP> , so that the original data pulse trains appear at A<SP>1</SP>, B<SP>1</SP>.