| 摘要 |
A regulated amplifier for supplying coded tone pulses from a communication line to the filters of a multifrequency decoding detector is made using directly coupled semiconductor elements for amplification and control. The gain of the amplifier is controlled by a light sensitive cadmium sulphide input series resistor illuminated by a gallium arsenide light emitting diode driven by the control circuit. An integrating amplifier stage is used to derive a control voltage from the output of the regulated amplifier, which voltage is modified by a temperature dependent reference voltage for compensating the temperature dependence of the light emitting diode. The control voltage is furnished to the stage that drives the light emitting diode through a coupling diode, so that a blocking voltage produced by an unregulated parallel channel of amplification-integration may be applied to the final control stage, to darken the light emitting diode and put the regulated amplifier in its minimum amplification condition when input signals are below the predetermined energy level.
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