Abstract: Apparatus for replacing conventional fault isolation resistors includes a terminal coupled to one winding of a transformer whose other winding is coupled across the two-line databus. Enhancement-mode-field-effect transistors have their source and drain electrodes each coupled between one end of the other winding and one of the databus lines and their control electrodes coupled at spaced intervals along the other winding. The winding voltage is zero when a terminal is not transmitting, turning off the field-effect transistors, presenting an open circuit. The parasitic body diodes of the transistors are connected in series and are poled to oppose each other to prevent conduction of signals from the databus. Thus, signals on the databus are not loaded by the terminal's output impedance. When winding voltage exceeds a threshold, one transistor conducts, providing substantially a short-circuit. The parasitic body diode of the remaining transistor also conducts.

Abstract: An integrated circuit device for comparing the state of a large number of inputs (i.e. "discretes") against any one of a plurality of selectable voltage levels. The compared data is examined in a 3.times.3 matrix format. In a redundant mode, comparators are utilized in a triple-redundant configuration to obtain a consensus on input states, at three successive time intervals, raising a flag when consensus fails. Inputs, whether in a redundant or non-redundant mode are distributed along three different sides of a rectangular-shaped substrate to prevent catastrophic mechanical failures. In the redundant mode, discretes are compared using a voting technique such that when all three levels are the same, an error free status is provided, whereas a two-out-of-three vote is interpreted as correct but with an indication that the discrete being monitored requires further checking.

Abstract: A bi-state linear amplifier is provided which, in response to a first state of a control signal, functions as a linear amplifier, and in response to a second state of a control signal, is cut off to define a high output impedance. The amplifier includes a control circuit responsive to relatively low-current control signals for selectively opening and closing the internal amplification circuit of the amplifier.