GB1196830A - Communication System. - Google Patents

Abstract

1,196,830. Digital transmission systems. ING. C. OLIVETTI & CO. S.p.A. 27 Nov., 1968 [26 Jan., 1968], No. 56370/68. Heading H4P. In a digital system comprising a central station and a number of remote terminal units, the terminals are all connected to a single modem which passes signals over a line to or from the central station. For simplex transmission over line L the modem is as at M2, Fig. 2a (part shown). When a signal is receved from the central station it passes via gate 40 and hybrid 44 to demodulator Dem. 2 which generates a "carrier detected" signal on line 9<SP>1</SP> 2 which passes via line 9<SP>11</SP> 2 to each terminal unit. Subsequently an address signal is received from the central station, this passing via line 4 2 to all the terminals. The addressed terminal responds by blocking gate 43 by a signal on line 24 2 to prevent further reception of data, and by enabling modulator Mod. 2 and blocking gate 45 by a signal on line 5 2 . When the modulator has reached its correct operating conditions it passes a signal over line 6 2 to the addressed terminal, and if the modem is ready to operate it passes a signal over line 7 2 . When the addressed terminal detects both these signals it transmits to the central station a signal indicating whether or not it is available for communication. In the case of a two way simplex system gates 43, 45 are omitted.