Abstract: An integrated logic circuit according to the present invention includes a plurality of logic circuit elements, such as field effect transistors, for performing a combinational logic function, and at least one test controlled-impedance element for loading the logic circuit and causing a first digital output signal to be produced when the impedance of a logic circuit element under test is within a predetermined range and produce another digital output signal when the impedance of the logic circuit element under test is outside the predetermined range. The test controlled-impedance elements typically comprise field effect transistors and are sized in accordance with a series of constraints. The constraints are obtained by considering the operation of the circuit under various impedance fault conditions (high, low and intermediate) and deriving a series of size relationships between the impedance values of the logic circuit and test elements.

Abstract: A system for use in providing compressed air for snow making equipment used in conjunction with a liquid cooled air compressor, including a plurality of motor driven fans and a heater coil assembly positioned in a portion of the path of the air moved by each of the fans, the heater coil assembly having a liquid coolant flowing therethrough, an air-to-air heat exchanger positioned adjacent the heater coil assembly and in the air flow paths of the fans, the air-to-air heat exchanger being connected in series with the air compressor and the snow making equipment and serving to reduce the temperature of the compressed air flowing from the compressor to the snow making equipment, actuator controlled louvers positioned above the air-to-air heat exchanger, there being one louver for each fan, a liquid cooling coil assembly supported adjacent the air-to-air heat heat exchanger and in a separate air flow path, a liquid transfer pump for moving cooling liquid from the compressor and a control assembly which may be a ma