Abstract: Disclosed is a low current binary input subsystem for providing a binary input signal to a data acquisition system. The binary input subsystem monitors the open/close state of a field contact and provides galvanic isolation of noisy field contacts, high noise immunity, a steady state current of approximately 1.2 milliamps resulting in power dissipation of approximately 0.25 watts for a 125 VDC input, and a momentary high current pulse of approximately 150 milliamps for a duration of approximately 4 milliseconds during field contact closure to aid in cleaning of oxides from the field contact.

Abstract: A rate converting bit stream demultiplexer and related multiplexer are disclosed. In the demultiplexer, there are two groups of N cascaded shift registers. A serial input data stream is alternately entered first into one of the groups of registers and then into the other. While the input data is being entered into one of the register groups, it is being simultaneously read from each shift register of the other group at a rate equal to the bit rate of the input data stream divided by N. In the multiplexer, the situation is reversed, with data being read from multiple input channels into each shift register in one group, while data is being read from a single output of the cascaded registers of the other group at a rate equal to N times the bit rate on the input channels.

Abstract: A variable displacement pump control having, in addition to a pressure compensator (with or without an auxiliary modulator), a multi-purpose valve which is open at pump startup to purge air therefrom, which is automatically closed after purging of the air, and which is opened in the manner of a relief valve responsive to a sudden rise in pump discharge pressure caused as by rapid closing of a directional control valve. The control is further characterized in that the pressure compensating pilot valve also constitutes a pilot valve for the multi-purpose valve to permit opening of a relief passage by the latter when pump discharge pressure suddenly rises.

Abstract: A current carrier communication system for selectively transmitting binary electrical signals from a first location to a second location over the AC power lines in a AC power distribution network in a building comprising a first tone generating means operatively connected to a first source of binary electrical signals for generating a first tone signal at a first frequency, a second tone generating means operatively connected to a second source of binary electrical signals for generating a second tone signal at a second frequency, linear tone summing means operatively connected to the first and second tone generating means for generating a modulating signal output that is a linear sum of the first and second tone signals, a source of RF signals connected to said linear tone summing means to produce a modulated RF output signal modulated by the modulating signal output of the linear tone summing means to the AC power lines, receiver coupling means at said second location directly coupled to receive said modula