Abstract: In order to assist persons of limited skill or time to test electromechanical or other relays without the need for VOM testing and time-consuming test setup, switching circuits, current sources are used in an automated test set with a stored program which tests the impedance between each terminal of the relay and every other terminal of the relay, identifies the terminals for the relay coil and for the relay's contact terminals and whether the contacts are NO, NC, or double throw type. The test set notes the presence or absence of a coil-suppression device across the coil, repetitively tests operation of the contacts, and informs the human operator, in simple terms, if the relay is operable and safe for use with delicate drive circuits.

Abstract: A motor has a rotor for controlling a parameter of an instrumentality, such as a blade or a blade flap. The rotor is positioned about the drive shaft of the instrumentality and rotates at the same average angular velocity of the drive shaft. The instrumentality is controlled by applying to the instrumentality a physical displacement signal that is generated by the phase relationship of the rotor of the motor with respect to the angular position of the drive shaft. A plurality of permanent magnets proximate the periphery of the rotor cooperate with a plurality of stator polepieces and electromagnetic coils. The current flowing through the coils is reversed each time that the rotor advances by the angular space of one permanent magnetic pole. The strength and polarity of the current flowing through the coils controls the direction and displacement of the rotor with respect to a neutral phasing of the rotor with respect to the drive shaft.

Abstract: A hot-plugging circuit for controlling the rate of application or withdrawal of both voltage and current to a user circuit to permit power up or down of the user circuit either to conserve energy usage in operation or to facilitate non-disruptive insertion or extraction of the user circuit from a larger, continually-powered, circuit. A semiconductor switch is used as the principle current and voltage control element. Current through the switch is monitored during transitions, and is converted to a voltage level. A voltage ramp relative to the voltage applied to the user circuit is generated and compared with the current representing voltage level to generate a control signal for controlling the rate of turn ON or turn OFF of the semiconductor switch. The voltage ramp generation is controlled by an ON/OFF control voltage level.

Abstract: A phase lock loop circuit (PLL) is manufactured as a part of each very large scale integrated circuit (VLSI) that might need clock pulses. When these VLSI chips are mounted on a printed circuit board (PC), three crystal oscillators are also mounted on the PC in order to provide redundancy. In order to identify crystal oscillators that are less desirable from the standpoint of operation and accuracy, a circuit is mounted on the PC for comparing oscillator frequencies and detecting when lack of frequency agreement is noted. A gating circuit receives the output of the detecting circuit for selecting and passing clock pulses only from a properly functioning crystal oscillator to the rest of the PC. Programmable counters are provided in the PLLs to allow local generation within each VLSI of clock pulses at a frequency that is a ratio of the frequency of the crystal-generated clock pulses that are circulated throughout the PC.