Abstract: A digital data and orderwire combiner employs a first and a second inverting gate amplifiers. The first amplifier receives the orderwire signal which is a low rate digital signal, while the second amplifier receives the data signal which is of a higher rate. The amplifiers have a common ground return where current through the amplifiers is directed through a resistive impedance network. The amplifiers as coupled together providing a 3-level amplitude modulated signal indicative of the combined data and orderwire signal. In order to reduce jitter, a portion of one of the signals is directed from one amplifier to the other. The configuration assure low jitter operation while producing reliable voltage levels indicative of 3-level amplitude modulation.

Abstract: A fault locating arrangement for a two-way repeatered transmission link comprising a source in one of the terminals to transmit a unique signal in a first transmission direction from the one of the terminals to the other of the terminals through the repeaters, and a first unique signal detector, a second unique signal detector and logic circuitry disposed in at least the other of the terminals and each of the repeaters. The first unique signal detector is coupled to the first transmission direction, the second unique signal detector is coupled to the opposite transmission direction and the logic circuitry is coupled to the first and second unique signal detectors such that, when the unique signal traveling in the first transmission direction is detected, a loop connection is established for the unique signal from the first transmission direction to the opposite transmission direction and the unique signal is transmitted in the first transmission direction beyond an associated one of the repeaters.