Abstract: A fault-location operating system for use with transmission networks using repeaters with loopback capabilities. A plurality of bidirectional transmission links L.sub.i, for i=1 through N, are used for transmission of data between the terminals. A test control unit is connected at the first terminal to the first end of the first transmission link L.sub.1, and controls transmission of control signals across the first transmission link L.sub.1. A plurality of repeaters R.sub.i, for i=1 through N-1, are used for interconnecting the plurality of bidirectional links. Each repeater R.sub.i is connected to the first end of one transmission link L.sub.i and to the second end of another transmission link L.sub.i+1. Each repeater includes a first circuit for repeating data transmitted from the one transmission link L.sub.i for transmission on the other transmission link L.sub.i+1, and a second circuit for repeating data transmitted from the other transmission link L.sub.

Abstract: A technique for measuring the value of a capacitance that is inseparatably connected with other circuit elements as part of a composite electrical circuit. The measurement is insensitive to such other elements that include resistances, inductances and active voltage sources. The technique involves the charging of the unknown capacitance followed by an immediate transfer of that charge to an external known capacitance that is part of an integrating circuit. The voltage stored by the known capacitance is unaffected by series resistances and is proportional to the desired electrical circuit capacitance being measured. The effect of induced or generated interfering signals in the circuit are cancelled by transferring the charge to the known capacitor for a period equal to an integral multiple of periods of the interfering signal. Furthermore, the charging voltage is adapted to the particular circuit in order to compensate for any resistance shunting the capacitance being measured.

Abstract: Centralized telephone circuit testing equipment with receptacles for selectively receiving a wide variety of electronic circuit modules, various modules being provided to make the equipment capable of performing a large number of commonly employed telephone tests. A scanning system is disclosed as part of the central measuring equipment for determining which of a plurality of remote testing stations has requested access to the central measuring equipment, one requesting remote station at a time being given complete control over a test function of the central measuring equipment for conducting tests on a telephone trunk.