Abstract: The disclosed voltage regulator circuit provides a regulated direct output voltage, across first and second output terminals, when an unregulated direct input voltage is applied across first and second input terminals. The second terminals are common to both input and output connections. A voltage reference device, having first and second electrodes, is connected so that the second electrode is connected to the second terminals. A first DC amplifier has an input circuit connected between the first input terminals and the first electrode, and an output circuit connected between the first output terminals and the first electrode. A second DC amplifier has an input circuit connected to the input circuit of the first DC amplifier and an output circuit connected to the output circuit of the first DC amplifier. The second DC amplifier, besides sharing the current load requirements with the first DC amplifier, also controls a bias current through the voltage reference device.

Abstract: A receiver is provided for utilization in a protective relaying modem to effectively distinguish between two mutually exclusive signal frequencies in a given frequency channel and which are respectively indicative of a "fault" or "no-fault" condition in a remote power transmission line. The received signals are coupled to a channel detector which utilizes a local oscillator and mixers to translate the received signal down in frequency so that simple low pass filters can isolate the desired frequency channel. The outputs of the low pass filters are operated on by a combination of multipliers and differentiators to generate an AM related output and a FM related output. The FM signal output of the channel detector is DC in nature and has an amplitude proportional to the deviation of the received signal frequency from the center frequency of the channel. This signal is used by separation circuitry to ascertain a fault or no-fault condition.