Abstract: A system comprises two kinds of multiplex stations connected by two wire lines and distinguished by two different predetermined frequency basebands each of which consists of predetermined frequencies for dividing the multiplex channels. The multiplex stations are provided with conversion means in their respective transmit paths so as to convert their own basebands to the different ones of the other multiplex stations connected and vice-versa. The system preferably provides generalized units in both kinds of multiplex stations and is simpler than a known one which uses the same basebands in all multiplex stations and converts the baseband before and after transmitting.

Abstract: Disclosed is an electronic signal processing system for an alternating voltage input signal. A phase-locked loop network has an input adapted to receive the signal and produce an intermediate signal comprising a substantially noise free sine wave with a phase equal to the average phase of the input signal. The intermediate signal is applied to an input of a variable gain amplifier which produces an output signal proportional to the intermediate signal, and an amplitude averaging loop network has the input signal and the output signal as its inputs and produces a biasing signal which is applied to a control input of the variable gain amplifier to maintain the output signal equal in amplitude to the average amplitude of said input signal. The system can be used in a Watson-Watt type radio direction finder to eliminate noise.