| 摘要 |
771,594. Voice frequency receivers. STANDARD TELEPHONES & CABLES, Ltd. July 10, 1953 [Nov. 3, 1952], No. 19228/53. Class 40 (4). In a communication system using out-ofband voice-frequency signalling, a receive amplifier dealing with the communication and signalling currents includes a reflex circuit arrangement whereby a predetermined harmonic of the signalling current is further amplified for actuation of the signalling relay. Incoming signals are applied to amplifier 1 over a transformer 3 and communication currents pass to terminals 7 over an anode transformer 4. The signalling current is selected by a tuned transformer 6 and harmonics thereof developed in a network 8 are applied to the grid of valve 1 via a potentiometer arrangement comprising a resistor R5 and the tuned primary of transformer 9. The amplified harmonic is selected by a tuned transformer 5 and applied via rectifiers Gl3, Gl4 to operating winding 12 of relay S. Changes of signal level and variations in the supply voltage are compensated for by a loading network 10 connected across the secondary of transformer 9 which network includes rectifiers Gl5, Gl6 biased by the difference between the operating voltage, and the hold voltage applied to the hold coil 13 of relay S. |
