Abstract: A thermal discriminator including two temperature sensitive switching devices having substantially identical electrical characteristics and exhibiting regenerative switching at a power level which is dependent on the temperature sensed by the switching devices. Both switching devices are exposed to the same ambient temperature in a surrounding medium but only one of them is exposed to variations in the heat exchange properties of the surrounding medium. Sufficient power is applied to both switching devices from an increasing voltage source to cause the switching devices to dissipate about the same amount of heat under certain conditions of the medium so that both switching devices would normally switch substantially simultaneously.

Abstract: The apparatus includes two temperature sensitive switching devices having substantially identical electrical characteristics and exhibiting regenerative switching at a power level which is dependent on the temperature sensed by the switching devices. Both switching devices are exposed to the same ambient temperature in a surrounding medium but only one of them is exposed to variations in the heat exchange properties of the surrounding medium. Means are provided for applying D.C. power to both switching devices at a level such as to maintain them below their switching point under preset conditions of the medium. A coupling device is interconnected between the two switching devices for inducing regenerative switching in one of the switching devices in response to unbalance in the heat dissipated by the switching devices due to variations in the heat exchange properties of the surrounding medium from the preset conditions.

Abstract: An adjustable temperature actuated switching apparatus using a fixed transition type negative temperature coefficient device is disclosed. Such device exhibits regenerative switching at a predetermined temperature and power level and a monotonic shift in the power level required to induce regenerative switching, this shift being a function of ambient temperature at the device. The apparatus comprises means for passing a controlled current through the device to thermally bias the same so as to make it switch at a desired ambient temperature at the device below its transition temperature, and means for detecting regenerative switching of such device as an indication that the desired temperature at the device has been reached. The source of controlled current may be a D.C. or an A.C. source.

Abstract: An apparatus for measuring an absolute temperature or a temperature differential. The apparatus uses two temperature sensitive switching devices exhibiting regenerative switching action at a power level which is dependent on the temperature sensed by such switching devices. Means are provided for simultaneously applying an increasing voltage to such switching devices to make them switch, and a detector is connected to both switching devices for measuring the time interval between switching of the first and second switching devices and for providing an output which is proportional to the absolute temperature sensed by the switching devices or to the temperature differential sensed by the switching devices. A display device is connected to the detector for providing a visual indication of the absolute temperature sensed or of the temperature differential sensed.

Abstract: An analog memory system is disclosed which uses a temperature sensitive device exhibiting a significant hysteresis centered about a predetermined transition temperature and a significant impedance change about such transition temperature to allow discrimination of a large number of identical temperature impedance levels with conventional electronic circuitry. The memory system comprises means for adjusting the temperature of such temperature sensitive device to write-in an input signal in the form of a predetermined impedance of said temperature sensitive device, means for subsequently adjusting the temperature of said temperature sensitive device at such transition temperature to store the input signal, and a converter for accurately converting the impedance of the temperature sensitive device to an analog of the signal stored in the memory system.

Abstract: A temperature control circuit is disclosed for controlling the firing angle of a thyristor such as a silicon controlled rectifier connected in series with a heater across an alternating power source. The control circuit comprises a field effect transistor having its source and drain electrodes connected for firing of the rectifier when the field effect transistor is rendered conductive, and a bias phase control connected to the gate of the field effect transistor for generating a fixed A.C. voltage component which is phase shifted by about 90.degree. with respect to the voltage of the power source together with a temperature dependent D.C. voltage component to control the firing angle of the silicon controlled rectifier in accordance with the heat generated by the heater, the sum of the A.C. and D.C. voltage components being fed to the gate of the field effect transistor. The temperature dependent D.C.

Abstract: A semi-conductor thermal protection arrangement is disclosed for use with class AB, B, or C power amplifiers or in any other circuit configuration wherein a reduction in drive signal at a stage prior to that of the protected semi-conductor results in a lessening of the protected semi-conductor dissipation. The arrangement comprises a temperature sensor thermally coupled with the protected semi-conductor for detecting the absolute temperature of the semi-conductor and electrically connected so as to reduce the drive signal of the semi-conductor when the temperature of such semi-conductor exceeds a predetermined temperature above the normal operating temperature of the semi-conductor.

Abstract: A temperature discrimination apparatus is disclosed which comprises a first switching device exhibiting regenerative switching action at a power level which is dependent on the temperature sensed by such first switching device, a second switching device exhibiting regenerative switching action solely in response to a pre-selected power level, means connected to the first and second switching devices for determining if the first switching device has switched before the second switching device in the cycle of the a.c. power source as the magnitude of the voltage increases from zero. This will serve as an indication that the temperature to be sensed has been reached.

Abstract: A solid state switching device comprises a temperature sensitive resistive element of V.sub.3 O.sub.5 material which exhibits an abrupt decrease in electrical resistance at about 140.degree.C and electrode lead wires attached to spaced points of such temperature sensitive resistive element for connecting the temperature sensitive resistive element to an electrical circuit.