Abstract: A pocket-size Time Domain Reflectometer is described. The pocket-size Time Domain Reflectometer consists of a pulse generator for producing a test pulse along with a delay line for delaying the test pulse before it is transmitted to a cable whose impedance characteristics are to be determined along its entire length. A test connector outputs the delayed test pulse to the cable that is being tested and the test connector receives reflections of the test pulse produced by the cable. The delay pulse generator produces a delay pulse having a pulse width identical to the test pulse at a time t after the production of a test pulse determined by the delay adjuster which is set in accordance with the specific point along the length of the cable which is being tested. A reflection sensing device is reponsive to the delay pulse and reflections received by the test connector and produces a reflection output signal which is monitored by a meter.

Abstract: Disclosed is a waveguide for conducting radio frequency signals along a railroad line comprising the ballast, ties and rails of the railroad line. If the waveguide is utilized for intra-train communication, the wheels, axles and under-vehicle parts of the vehicles of the train comprise the side and upper surfaces of the waveguide. The waveguide may be utilized to: (1) transmit data such as train vehicle journal bearing temperatures, from remote locations to either the caboose or engine of the train; (2) guide radar-type radio frequency pulses ahead of the train; or (3) transmit any other data. In the radar embodiment, reflections received by a receiver on the train represent changes in the characteristic impedance of the waveguide. These reflections may be compared to anticipated reflections in order to detect improper conditions such as broken track or the presence of another train.