Pilot tone monitor for carrier frequency systems - has successive gain adjustment via flip=flops from low to high gain with specified adjustment for instances of missing pilot

摘要

The pilot tone monitor circuit for carrier frequency transmission systems comprises a level detector, regulator and alarm circuit (PR) with four terminal points (VE1-2, AA-AB). A single transistor stage (TSV) operates as a presetting device with a zener diode in its base circuit. Two further transistors are connected as a bistable circuit (TS1-2). The regulating system is initially set to a relatively low order of gain, and then is successively adjusted to higher gain. If the pilot tone fails, the regulator is set so that the gain exceeds and is then maintained at the difference between the setting range middle value and the alarm level/average value difference. The flip-flop is self-interrogating so that this regulator setting is detected.