GB705813A - Translator for electric pulse code communication systems - Google Patents

Abstract

705,813. Pulse code modulation circuits. STANDARD TELEPHONES & CABLES, Ltd. (Federal Telecommunications Laboratories, Inc.). Aug. 1, 1952, No. 19514/52. Class 40 (5) Time modulated pulses are converted into pulse code groups by providing a scanning pulse train of the same recurrence frequency, a plurality of normally blocked coding circuits all connected to one of the pulse sources and one or more delay devices, connected to the other source, which sequentially condition the coding circuits. In one embodiment, a seven-level, three-unit simple addition binary coder comprises three normally blocked valves 32 ... 34, to which are applied simultaneously, over lead 51, the time modulated pulses from modulator 49. Any code pulses which are, at the same time, applied over leads 35 ... 37 respectively to the individual valves, then unblock them, the pulses being applied in succession to lead 56 through a distributer 55 to produce a code group. To produce the succession of pulse combinations on leads 35... 37, a pulse 58 from generator 47 is applied to a delay line 38 having equally spaced tappings 0 ... 6. The leads 35 ... 37 are connected in different combinations through resistances 57 to these tappings, so that at the instant when a time modulated pulse occurs a specific combination of valves will be receiving code pulses depending upon the modulating signal amplitude. The duration of pulse 58 is substantially equal to the delay between adjacent tappings on line 38. The switches 48, 50 may be operated to apply the modulated pulses from generator 49 to the delay line 38 and the unmodulated pulses from generator 47 to lead 51. The tapped delay line may be replaced by individual delay lines between the points 0-1, 0-2 &c. The invention may be applied to coders using any type of code with any number of units. Volume compression may be effected by causing selected extreme values of signal to produce the same code group, groups of adjacent tappings on the delay line being connected together for this purpose, Figs. 5, 6 (not shown). Specification 535,860 is referred to.