Abstract: Circuitry includes a circuit path that corresponds to a channel of system for testing a device, an element in the circuit path, a first device to measure an electrical parameter associated with the element, a second device to obtain an error signal associated with the channel, and a feedback path electrically connected to the second device to pass the error signal or another signal.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. In a preferred embodiment, a tuning network is connected between the two amplifiers for optimizing the amplification of a selected band of radio frequencies.