Receiver unit for remote pipeline surveillance system - operates with two signal channels containing amplitude modulator and frequency discriminator

摘要

The remote surveillance system for pipeline sections uses a receiver unit receiving LF and ULF signals and with a filter (3) which employs an AC amplifier (4). The input of the latter is connected to the filter output and its output is connected via an amplitude modulator (5) and a DC amplifier (6) to a threshold circuit (8). One signal channel contains an integrator (7) inserted between the amplitude modulator (5) and the threshold circuit (8) while a second signal channel includes a frequency discriminator (10). One input (11) of the latter is coupled to the amplitude modulator input end its output is connected to an AND gate (12) also connected to the output of the threshold circuit (8). A reset pulse generator (15) is connected to the other input of the frequency discriminator (10) and controlled via the AND gate (12).