Abstract: The invention describes an internal test load and method for forming an internal test load which is adapted to absorb energy from a power source such as an RF transmitter, transceiver, or amplifier. The test load is positioned internally within a housing, and includes at least one impedance device, such as a power resistor, coupled to the power source which is matched to the impedance thereof. The impedance device is supported on a heat sink which is adapted to absorb heat generated by the impedance device so as to be distributed over a relatively large area constituting the heat sink. The heat sink is positioned in spaced part relation to the housing, and is not directly supported or secured to the housing. A potting material surrounds the load assembly and supports the heat sink, wherein the heat sink effectively "floats" within the potting material such that heat absorbed by the heat sink will not be directly transferred to the housing, but will be dissipated through the potting compound.

Abstract: The invention described a pocket size antenna VSWR indicator having a self-contained low level wideband RF signal source which is applied to an antenna under test through a four arm RF resistive bridge circuit. The bridge circuit has been designed to be very accurate and reliable and provides a novelly positioned reference against which the reflection co-efficient of the transmission system is compared to reliably indicate the VSWR of the system. The bridge circuit provides a flat response over the desired wideband frequency range and over the range of antenna impedances which may be encountered. The RF null or bridge balance is detected in a radio receiver or transceiver tuned to the desired operating frequency, from which an indication of antenna VSWR may be provided. The antenna VSWR may be indicated in a variety of way, such as by means of a numbered or colored dial, a plurality of LEDs or an audio tone shift against an internal reference.

Abstract: A phase-triggered, gate-controlled AC semiconductor switch of the thyrister type in series with an induction motor and its AC supply, optimizes power flow to the motor under changing mechanical load conditions by varying the amount of supply voltage applied to the motor over each half-cycle of the AC supply. The triggering point of the semiconductor switch relative to the preceding zero crossing point of the supply voltage, that is, the switch firing angle or delay angle, is varied as a function of mechanical loading on the motor by means of a load current induced feedback voltage which varies the breakdown or triggering voltage of a two-transistor switch functioning as a variable trigger diode between the gate of the semiconductor switch and a turn-on capacitor charged by the AC supply voltage during non-conducting periods of the semiconductor switch.

Abstract: A radio receiver equipped central control unit continuously monitors at least one battery-powered remote transmitter activated in response to predetermined alarm conditions, such as open doors and windows, fire, smoke, low transmitter battery voltage, and the like. In its activated condition, the transmitter is cycled to radiate a one-second duration radio frequency signal every 30 seconds, such cycling being established by transmitter timer circuitry series-inserted between the transmitter and its battery power source. The transmitted signal is received by the central control unit which, in response to the received signal, selects and activates one or more alarm indicators for a predetermined time period. Such selection and activation of particular alarm indicators and the duration of their activation are determined by switching and timing circuitry series-inserted between the central control unit's radio frequency receiver and the various alarm indicators.