SIMPLE LOW COST TIME DOMAIN REFLECTOMETER.

A circuit is described which was designed to provide a low-cost means of spacially locating open or short circuit faults in long runs of uniform cable, requiring only a moderately fast laboratory oscilloscope (T//r less than 20 ns) with a TTL compatible sweep gate pulse output, and a plus 12 volt dc power supply. The circuit operates by sending a voltage pulse into the cable under test, subsequently detecting any reverse polarity reflections from discontinuities in the line; the temporal displacement (t) between the send and receive pulses yielding a measure of the fault distance from the test point.