GB628260A - Method for the duration modulation of electric pulses - Google Patents

Abstract

628,260. Pulse modulation multiplex pulse signalling. SADIR-CARPENTIER. July 31, 1946, Nos. 22873, [Convention date, July 31, 1945], 22874 and 22875, [Convention dates, Aug. 1, 1945]. [Class 40 (v)] Amplitude-modulated pulses fed across a resistance 14, Fig. 3, from a modulated valve 8, are converted into duration modulated pulses beginning at the commencement of the amplitude-modulated pulses and terminating when a sawtooth voltage obtained by the charging of a condenser 15 from a constant current generator 17 reaches a positive value equal to the negative voltage produced by a pulse across the resistance, a diode 16 or other valve with anode connected between the condenser 15 and generator 17 then returning to a normally conducting state. The duration modulated pulses produced during blocking of the diode 16 pass through a valve 18 and a pulse shaping member 19. The diode may be omitted if the grid cathode resistance of the valve 18 is low. The pulses are produced by a constant amplitude pulse generator 9 and are amplitudemodulated by the valve 8 using suppressor grid injection of the modulating voltage from a source 10. Alternatively, Fig. 5, the amplitudemodulated pulses from the modulator valve 23 are fed to an anode resistance 30 connected across the grid and anode circuit of a valve 29 having between its anode and cathode a charging condenser 28, and a resistance 34 in its anode lead. Constant amplitude pulses are fed from a generator 9 to the grids of a valve 22 and of the modulator valve 23. The valves 22, 23 are normally blocked and the condenser 28 uncharged, but on the valves receiving a positive pulse the condenser 28 charges from the triode or pentode 22 until the voltage across it becomes equal to the voltage across resistance 30 due to the amplitude-modulated pulse from the valve 23 (disregarding the negligibly small cut-off bias of the valve 29). The durationmodulated pulse commences at the instant when the valve 29 conducts, is taken off across the resistance 34, and continues till the pulse from the generator 9 ceases, the valves 22, 23 then becoming blocked again due to the negative charges acquired by the grid sides of the condensers 24, 26, the condenser 28 at the same time quickly discharging across the valve 29. Multiplex transmissions may be obtained using circuits as in Fig. 3 and a delay line 42 (Fig. 12, not shown), from tappings on which various pulse amplitude-modulator valves, one to each communication channel, are fed, the valve feeding a common resistance 52, charging condenser 53, diode 54 and constant current generator 55 duration-modulating the pulses, and a mixer 49 receiving direct from the pulse generator the synchronizing signal. Alterna. tively circuits as in Fig. 5 may be used (Fig. 13, not shown).