Monitoring circuit for carrier systems - has two differential amplifiers, with pilot signal applied to first, and output signal delivered by second

摘要

The circuit monitors pilot and carrier frequencies and delivers an alarm signal when they exceeds their limits. Two differential amplifiers have transistors of different conduction types. One input of each amplifier is connected to a tapping of a voltage divider, and at least one rectifier pilot voltage is applied to the second input of the first amplifier, while the second amplifier second input is connected to the output of the first amplifier. Decoupling diodes are connected to the amplifier inputs, and between the voltage divider tappings and the first inputs of the amplifiers. A signal is delivered by the second amplifier output.