Abstract: A time domain reflectometer apparatus for testing a cable and for cooperation with an oscilloscope or other display apparatus which includes structure for generating a first plurality of pulses which are positive going and for generating a second plurality of pulses which are negative going and which are each synchronized with one of the positive going pulses. The apparatus also includes structure for applying at least one of the pluralities of pulses to a cable to be tested, for cooperating with the associated display apparatus, for providing a display of at least reflective pulses from the cable being tested and for bucking the positive going pulses with the negative going pulses to minimize the amplitude displayed of the pulses being supplied to the cable being tested.

Abstract: In an electrical multi-channel signal transmission system having channels with signal carriers of predetermined frequencies, each frequency is an integral multiple of a constant which is a measure of frequency spacing between channels with the addition or subtraction of an integral multiple of one or more other constants. The integral multiples of the one or more other constants are selected to cause the frequencies of significant intermodulation products produced by simultaneous treatment of carriers by electrical components, such as amplifiers, to be equal to other carrier frequencies. The frequencies are obtained from a plurality of oscillators with frequencies related to the constants. The invention is especially useful with cable television systems transmitting programs on low, mid and high band channels.