| 摘要 |
A fault detection and locating test instrument for indicating wiring and station equipment faults on telephone lines, such as grounds, foreign batteries, resistance across lines, and open circuits. It can be portable or wired, and required no internal power source. Visual display or detected faults are by means of light-emitting diodes. A feature of the instrument is an output circuit including a pair of connected transistors associated with light-emitting diodes for indicating current flow or lack thereof, and a capacitor-diode circuit for indicating presence of an alternating current at the output terminals. An input test circuit also provides an indication of the presence of the normal voltage and its polarity supplied by the telephone company. A jack connection is provided for to enable normal use of the lines when the instrument is connected and as fault appears at the output. A reversing switch in the output can be used to test the telephone set capacitor to determine whether or not the line is open.
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