| 摘要 |
<p>659,806. Pulse modulating. STANDARD TELEPHONES & CABLES, Ltd. May 12, 1947, No. 12769. [Class 40 (v)] [Also in Group XL (a)] A pulse time modulator comprises a coldcathode gas discharge tube (see Group XL (a)), with a maintaining potential insufficient to initiate a discharge, applied to the main discharge gap, means for periodically firing the gap at times depending on the signal voltage and means for periodically extinguishing the discharge. In one embodiment, durationmodulated pulses are produced in transformer 6, Fig. 1, connected in series with the main anode 2 and cathode 3 of tube 1. The maintaining potential is applied to anode 2 from source 7 and negative extinguishing pulses (a), Fig. 2, through condenser 15. The firing waveform (b) is applied to an auxiliary anode 4, through circuit 16, 17, and is modified by the signal voltage applied to transformer 12 connected between the anode 4 and a tapping on voltage source 7. If the signal wave (c) is added to waveform (b) the resultant (d) causes the tube to fire at times q, r, s, corresponding to the voltage v3 and the negative going pulses of waveforms (a) and (d) extinguish the tube at the times B, D, F, giving rise to duration modulated current pulses (e) through the transformer 6. Circuit 9, 10 provides negative feed-back of the signal voltage to the signal input circuit for distortion correction. In a modification, Fig. 3 (not shown), a similar circuit produces frequency modulated pulses, the control voltage waves being omitted and both discharge paths being self-squegging, due to the provision of squeg resistances. Specification 659,805 is referred to.</p> |
