A circuit arrangement for producing signals of predetermined amplitude and duration,in dependence on pulse code modulated signals

摘要

1,028,430. Transistor pulse shaping circuits. TELEFONAKTIEBOLAGET L. M. ERICSSON. March 21, 1963 [March 21, 1962], No. 11349/63. Heading H3T. [Also in Division G4] In a circuit for regenerating pulse code modulated signals, e.g. in a decoder, the seven-digit binary signal P1, Fig. 1 (not shown), is converted into parallel form in a tapped delay line FL whose respective outputs are connected via gates G1 to G7, controlled by timing pulses P2, P3, to electronic switches S1 to S7. The electronic switches provide pulses of constant amplitude and duration which are added in a resistance network RN in known manner to provide an analogue output. Fig. 2 shows details of the output of a portion K1, K2 of the delay lines FL. In the absence of pulses P1, P2, the diodes D1, D2 in the gate G1 are conducting so that point A is at zero potential and transistor T1, in a regenerative amplifier forming electronic switch S1 is blocked. When pulses P1, P2 occur simultaneously, the diodes D1, D2 are blocked, the 6 volts potential at point A causes transistor T1 to conduct and the regenerative feedback causes the potential at point A to fall and diode D3 to conduct. This causes an increase in the base current of transistor T1 and consequently an increase in the collector current providing an output signal at point C. To ensure that all output pulses have the same duration an inhibiting circuit H including a transistor T2 is controlled by pulses P3. In the absence of pulses P3 the transistor T2 and diode D4 are blocked and have no effect on the circuit S1. When a pulse P3 is fed to the base of the transistor T2 it will conduct and the resulting fall of potential at the collector will cause D4 to conduct and block transistor T1, the output pulses in all the circuits S1, S2 &c. ceasing simultaneously. A diode D5 in the collector circuit of transistor T1 eliminates the voltage peak which would arise due to the interruption of the current through the winding of transformer TR.