GB799150A - Improvements in or relating to pulse transmission systems - Google Patents

Abstract

799,150. Pulse modulation circuits. TELEFONAKTIEBOLAGET L.M. ERICSSON. March 16, 1956 [March 16, 1955], No. 8352/56. Class 40 (5,). In a multi-channel pulse communication receiving system an abnormal pulse in a regular pulse train, Fig. 2a, is detected by applying the pulses, Fig. 2b, and a wave of pulse recurrence frequency, Fig. 2c, to a gating circuit. The pulses, Fig. 2a, applied between 0 and 1, Fig. 1, are reversed in polarity at the anode of V1 and applied to the gating circuit comprismg diodes D1, D2 and transformer T. The high-Q resonant circuit L1, C1 tuned to the pulse recurrence frequency maintains by means of the feed-back winding L2 an unvarying sinusoidal voltage, irrespective of the appearance of an abnormal pulse, whose maximum negative value concides with the negative pulses except when an abnormal pulse appears. The anode of D2 is given a lower bias voltage than the cathode of D1 both diodes thus being blocked, and normally no current passes through T. The abnormal pulse appears as a negative pulse on the cathode of D1, the anode of D2 being simultaneously fed with the positive half-cycle of the sinusoidal voltage. The diodes thus conduct for the duration of the abnormal pulse and current passes, and the pulse appears, Fig. 2d, at the output winding of T. In a further embodiment, Fig. 3, a positive pulse train, Fig. 4a, is fed to the control grid of V3 which is biased to cut-off for the duration of the applied pulses causing a sinusoidal voltage at the resonant circuit L1, C1. The voltage of the suppressor grid inductively coupled by winding L2 varies in phase with the screen voltage, Fig. 4c. Applied pulses normally appear when the screen and suppressor grid voltage are minimum, the suppressor grid voltage being lower than the cut-off voltage V-stryp, Fig. 4c, of the suppressor grid so that no anode current flows. An abnormal pulse occurs when screen and suppressor grid voltages are maximum, thus causing anode current to flow and pulses to appear at output terminal 2. An application of the invention to a multi-channel pulse system comprising two terminals and intermediate relay stations, and a subroute between one relay station and a third terminal, is described wherein the channel-pulses to be branched are selected at the relay station, their time positions being such that their pulses appear in the middle of the respective pulse intervals.