Pilot controlled repeater for analogue transmission system - automatically compensates for changes in analogue signal level

摘要

A repeater (1) amplifiers a range of analogue signals and a pilot signal. A filter (2) passes the pilot signal through an amplifier (3), and a rectifier (4), to one input of a differential amplifier (5). Feedback from the output of the differential amplifier is through a resistor (6) back to its second input. The feedback voltage (V1) is also a function of a fixed reference voltage (Vref). The circuit can automatically compensate for changes in the repeater input signal due to temperature changes in the cable. An alternative version has feedback from the comparator output to the pilot signal amplifier.