Wiltron Company

Duane E Dunwoodie

Paul R Bauer

Walter A Lobitz

Paul A Marshall

Clarence E Elkins

Mohamed M Mansour

Ker-Chin Chang

Wallace Oliver

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.i+1 for transmission on the one transmission link L.sub.i. In addition, a loopback circuit is included in each repeater that is responsive to the control signals on the one transmission link L.sub.i for looping back data transmitted from the one transmission link L.sub.i for transmission back on the one transmission link L.sub.i. In this system, each repeater has a loopback capability responsive to control signals sent through the transmission links. The loopback capability can be provided in other elements in the network so that a single test control unit can be used to located faults anywhere within the network.

Fault location operating system with loopback

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. Improvements are also disclosed in the individual test function electronic circuit modules, including common circuits for use in measuring both signal level and circuit noise, a logarithmic analog-to-digital convertor capable of handling signals that cross zero dBm in level, round off digital display circuits to improve accuracy of the display and to aid in calibrating the instruments, and an improved frequency measuring circuit.

Telephone system testing apparatus and techniques utilizing central

A movable telephone circuit test instrument is provided, indicators mounted thereon which show the communicating state of a telephone circuit being tested. Supervision of the circuit under test is thus provided at the same location as the tester, thereby reducing the number of persons required to carry out the test. The supervising indicating means are preferably light emitting diodes and are provided in a unique driving circuit that includes a variable conductance parallel current path for maintaining the brightness of the light emitting diode substantially constant regardless of the magnitude of current being monitored by the supervising circuits.

Telephone line testing instrument having a supervising capability

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Los Altos, CA, United States of America

Duane E Dunwoodie