Abstract: A thermal processor for thermally processing a sequence of exposed photothermographic media comprising: a rotatable thermally conductive drum; a heat source for heating the drum to a setpoint temperature; a plurality of rollers spaced around a portion of the periphery of the drum for holding down exposed photothermographic media to the drum for thermal development thereof; a sensor for sensing the temperature of the drum; and a control for controlling the temperature of the drum as a function (1) of the setpoint temperature, (2) of the sensed drum temperature, and (3) of the status of the processor, i.e., whether or not photothermographic media is being processed by the drum, in order to compensate for heat loss due to media heating and roller heating.

Abstract: A heater temperature control circuit for controlling a temperature of, for example, a heater incorporated in a laser printer for fixing a toner image on a recording material includes a voltage divider circuit delivering an output voltage divided by a thermistor changing a resistance value thereof in response to temperature changes with generation of heat by a heater and a resistance having a predetermined resistance value, and a heater control circuit comparing the output voltage of the voltage divider circuit with a reference voltage, thereby delivering a control signal for controlling an amount of heat generated by the heater on the basis of results of comparison.

Abstract: A control device for a heater for an air fuel ratio sensor attached close to a sensor element of an air fuel ratio sensor located in an intake passage of an intake passage.The control device comprises an ambient temperature related parameter detecting means for detecting a parameter related an ambient temperature of the air fuel ratio sensor, an intake air amount related parameter detecting means for detecting a parameter related amount of fresh intake air introduced into intake passage, and supply power controlling means for controlling supply power based on a parameter detected by an ambient temperature related parameter detecting means and a parameter detected by an intake air amount related parameter detecting means.

Abstract: An electric resistance heating element preferably of cylindrical or prismatic shape to be inserted into a test tube, a cartridge or in another cavity has one or more conductors connected to the supply system by the use of one or more electrodes. The conductors are made of a conductive composite material of a polymeric matrix with resistive function which are formulated at such ratio and materials as to achieve an electric resistance with high positive temperature coefficient (PTC) at the operation temperatures. The electrodes may be made of metallic materials. At least a core is made of insulating material, onto which the conductors with resistive function (PTC) and the electrodes are applied.

Abstract: An integrated circuit constructed to provide control functions to a toaster oven cooking appliance. The control functions including compensation for input voltage fluctuations, compensation for residual heat due to recycling, audible signal generation, multiple mode selection, safety shut off and others. The integrated circuit also provides flexibility to accommodate multiple models of an appliance in a product line.

Abstract: A heating panel has a substrate with a resistive heating material disposed thereon. The substrate can be metal with an insulating layer disposed between the substrate and the heating layer. Alternatively, the substrate can be glass ceramic. The heating layer has electrodes on opposite edges connected to different phases of a multiphase power source. Another electrode on the heating layer can be connected to a neutral of the power source. Capacitive currents caused in the substrate or a metal object on the substrate by the different phases cancel each other. Thus, leakage current through a conductor connected between the substrate and ground is minimized. The heating panel can be adapted for two phase or three phase systems. Power to the panels is controlled by solid state switches or relays. Zero crossing drivers sense supply voltages and operate the switches to balance currents in the panels.

Abstract: A novel multi-layer current limiting PTC polymer device comprising at least two layers of a conductive polymer composition with electrodes attached thereto characterized by having a low contact resistance and a method of producing the same. The invention provides for the selective treatment of portions of the surface of each layer of the conductive polymer composition by at least one of plasma/corona etching and plasma sputtering/plasma spray to create a site for attachment of the electrodes resulting in a low contact resistance. The electrical devices of the invention are particularly useful in circuit protection applications.

Abstract: A melt-extrudable conductive polymer composition which contains a polymer, a particulate conductive filler, and a particulate nonconductive filler. When a standard strip heater is made from the composition and tested in a UL VW-1 test, it has comparable performance to a heater made from a second composition which is the same as the composition but which does not contain the nonconductive filler. When tested in a standard arcing fault test, the standard heater will trip a fuse in less time than is required by the second heater, i.e. in less than 30 seconds. In some embodiments, the composition also comprises a flame retardant, preferably a halogenated flame retardant. When strip heaters prepared from these compositions are tested in a standard arc propagation test, an arc will not propagate. A preferred nonconductive filler is Sb.sub.2 O.sub.3.

Abstract: Self-regulating heating element for heating a gaseous flowing medium with a strip conductor (1) and a control conductor (2) which are electrically connected to one another in series and are in thermal contact with one another over their length, but which are electrically insulated from one another. The Control conductor (2) is preferably formed of a jacketed conductor with a metallic jacket which is electrically connected to the strip conductor (1).

Abstract: The invention is directed to a positive temperature coefficient heater. A pair of electrical conductors are connected to a positive temperature coefficient body at respective locations. A dielectric material is attached to the body between the conductors and prevents electrical arcing around the body between the conductors.

Abstract: The present invention generally relates to use of constant current power supply to control temperatures of a device to plural Curie temperatures, without sacrificing the precision and uniformity of temperature achieved in the known devices. In accordance with exemplary embodiments, multiple layers of alloy having different Curie temperatures are separately accessed as an outer most layer is heated through its Curie point. Power to the device can be controlled by varying a frequency of circulating current and by searching to identify a layer of Curie point material which provides heating at a temperature accurately controlled to a fixed value, where any one of a number of different such temperatures may be selected.

Abstract: A ceramic heating element has been conventionally driven by direct-current voltage, but the direct-current voltage causes a problem in the heating element. Therefore, in a method of the present invention, an alternating current is supplied to the heating element by changing a direct current, so that deformation of the heating element can be prevented and reliability can be improved.

Abstract: The present invention provides methods of calibrating a deposition device, which is preferably a vapor deposition device, and more preferably is a physical vapor deposition device. One of the methods includes the steps of: (1) determining a resistance-temperature relationship of a substance located on a semiconductor wafer, a resistance of the substance being a function of a temperature of said semiconductor wafer; (2) placing the semiconductor wafer in the deposition device; (3) heating the heater to a known temperature; and (4) measuring a resistance of the substance, the resistance-temperature relationship allowing a relationship between a temperature of the semiconductor wafer and the known temperature to be determined, thereby to allow the deposition device to be calibrated.

Abstract: A steamer for a steamable hair curler includes thermally isolated cold and hot water reservoirs. Water in the hot water reservoir is heated by a PTC heater. The volumetric t capacity of the hot water reservoir is very small. The PTC heater has an intrinsic cutoff temperature high enough to boil water in the hot water reservoir and low enough to prevent deterioration of any component parts of the steamer, even in the absence of water in the hot water reservoir. Due to the thermal isolation of the reservoirs, water in the cold water reservoir is not substantially heated during normal operation of the steamer.

Abstract: An electrical heating device employing positive temperature coefficient (PTC) thermistors as heating elements, which provides direct contact between the thermistor heating elements and the radiation units on both sides with no intervening members and which also provides the electrical current to the heating elements via the radiation units.

Abstract: A novel current limiting PTC polymer device and methods of making the same comprising a current limiting polymer composition with porous electrodes interfaced therewith such that a low contact resistance results using a combination of (1) extrusion attachment of the current limiting polymer composition to the porous electrodes, (2) careful selection of the electrode materials in view of the conductive filler and/or conductive metal particles in the current limiting polymer composition, and (3) plasma treatment of the attachment surfaces of the current limiting polymer composition preceding and/or during the extrusion attachment process. The invention provides for the selective treatment of portions of the surface of the current limiting polymer composition by at least one of plasma etching and metallizing to create attachment surfaces for extrusion attachment of porous electrodes resulting in a low contact resistance, mechanical stability and a reduced potential for arcing in the electrode/polymer interface.

Abstract: A temperature regulated manicure bowl is provided having a temperature control channel and an heating channel. The heating channel is provided to heat water to a preset temperature level. The temperature control channel is provided to control the heating channel, thereby regulating the temperature of the water. The temperature regulated bowl is also provided with a monitoring channel that monitor's the temperature control channel and the heating channel to insure proper operation. Additionally, a disposable sheath is provided to fit over the bowl. The disposable sheath is a means to prevent the spreading of hand born infections.

Abstract: An automatic control system controls a controlled variable serving as an object 2 to be controlled so that the object 2 approaches a predetermined target value, by means of an optimum regulator 4. The automatic control system include: a gain setting section 48 for setting a gain; a comparing section 48 for comparing the target value with the controlled variable serving as the object; and a weight control section 50 for weighting the gain set by the gain setting section so as to increase the weight from 0 to 1 within a predetermined period of time and for deriving a corrected manipulated variable in response to the time when a difference between the target value and the controlled variable comes within a range of a predetermined percentage of the target value, so that the corrected manipulated variable is added to the manipulated variable derived by the optimum regulator.

Abstract: Apparatus for detecting working fluid state in a heat transfer system of the type having an evaporator and an expansion valve for controlling mass flow of the working fluid to the evaporator, comprises a first sensor disposed in the working fluid on the outlet side of the evaporator; the first sensor producing a first signal related to the working fluid state; a second sensor disposed in the working fluid on the inlet side of the evaporator; the second sensor producing a second signal related to a pressure dependent characteristic of the working fluid; and a control circuit for receiving the first and second signals and determining the working fluid state based on a ratio of the first and second signals.

Abstract: Electric steam iron having a hot part (1) composed of a sole (7) and a steam chamber (4), the sole having a portion situated under the steam chamber, and the hot part (1) of the iron being subdivided into at least two thermal zones. A plurality of heating elements are each disposed to heat a respective one of the thermal zones and a plurality of regulation organs are each associated with a respective one of the heating elements. The at least two thermal zones include a first thermal zone (A) having at least one surface corresponding substantially to the steam chamber (4) and a second thermal zone (B) having at least one surface corresponding substantially to the portion of the sole situated under the steam chamber, the first thermal zone (A) and the second thermal zone (B) being in thermal communication with one another. The heating element which is disposed to heat the first thermal zone is arranged to at least partially heat the second thermal zone.

Abstract: An improved heater wire and electro-thermal controller suitable for use in electric heating appliances such as electric blankets and heating pads. The heater wire is formed with a first conductor for heat generation and a second conductor for sensing. The first conductor and second conductor are wound as coaxial spirals with an insulation material electrically isolating the two conductors. The two spirals are counter-wound with respect to one another to insure that the turns cross, albeit on separate planes, several times per inch. With the conductors thus formed, if the insulation separating the conductors fails, the first and second conductors will come into electrical contact to facilitate detection of this hazardous condition. The controller of the present invention includes an electronic control unit a sensor input circuit, a heater driver circuit and a user interface circuit.

Abstract: A PTC (positive temperature coefficient) thermistor heating apparatus includes two or more heating blocks, each heating block including a PTC thermistor and radiating elements disposed in contact with at least two surfaces of the PTC thermistor; an elastic element disposed between the heating blocks; and insulating elements for holding portions of the radiating elements at the ends of the heating blocks; wherein the heating blocks are biased from each other by an elastic force of the elastic element.

Abstract: The temperature of a heating element (3), which heating element has a temperature dependent resistance, is measured by comparing the current through it with a user adjustable reference value. The AC voltage across a current sensing resistor (7) in series with the heating element (3) is compared in a comparator (9) with a reference AC voltage generated at a tap (6) of a voltage divider (8). The phase of the logic output signal of the comparator (9) indicates a first state in which the heating element (3) is too hot or is not conducting, or a second state in which the heating element (3) is too cold and conducting. A second comparator (16) detects whether or not the heating element (3) is conducting. A logic gate (18) and a latch (17) switch on the current through the heating element (3) in response to timed pulses from a timing circuit (15) and switch off the current through the heating element (3) when the heating element (3) is conducting and too hot.

Abstract: Electrical devices based on current limiting PTC polymer devices, and in particular, electrical circuit protection devices containing a current limiting PTC polymer device composed of a current limiting polymer composition in combination with suitable electrodes and a low inductance shunt to protect the current limiting polymer composition from exceeding its breakdown field strength. Specifically, electrical devices containing a current limiting polymer composition in combination with suitable electrodes and a low inductance shunt in the form of a ribbon shunt, i.e. a flat sheet of conductive material folded over on itself.

Abstract: A novel current limiting PTC polymer device comprising a conductive polymer composition with electrodes attached thereto characterized by having a low contact resistance and a method of producing the same. The invention provides for the selective treatment of portions of the surface of the conductive polymer composition by at least one of plasma/corona etching and plasma sputtering/plasma spray to create a site for attachment of the electrodes resulting in a low contact resistance. The electrical devices of the invention are particularly useful in circuit protection applications.

Abstract: A temperature control heater with sink type glass tube liquid crystal (LCD) display, especially relates to a temperature control heater having a structure for display the temperature precisely, the mainly structure thereof is comprised of a single opening tube, and a liquid crystal (LCD) display temperature control circuit board and a heating coil set is arranged with said tube, finally a plug and a cover are used to tightly seal the tube.

Abstract: A heater unit 1 has a plurality of flat heaters 11 adjacently arranged side by side and having common upper and lower surfaces. The thickness T of the heaters 11 is substantially uniform. Each heater 11 has an adjacent end surface 111 which faces toward an adjacent end surface 111 of the adjacent heater 11. The heater unit 1 also has upper and lower electrodes 21 holding the heaters 11 and respectively attached to the upper and lower surfaces of the heaters 11. The adjacent end surfaces 111 of the heaters 11 adjoining each other, and the upper and lower electrodes 21 form an air gap 12 therebetween. The creepage distance L along each adjacent end surface 111 is larger than the thickness T of the heaters 11. The dielectric strength of the heater unit 1 depends on the creepage distance L. The thickness T of the heaters 11 can be decreased without decreasing the dielectric strength of the heater unit 1. The output of the heater unit 1 increases when the thickness T is decreased.

Abstract: The present invention is a heated wiper blade comprising an elongated blade and a heating element connected to the electrical system of a vehicle. The heating element utilizes a material with a positive temperature coefficient of resistance placed between a pair of conductive members. The conductive members span the length of the heating element to provide a uniform distribution of heat through the length of the blade. Electrical connections to the heating element are preferably located at one end of the blade. The heating element can be located inside the blade or between a semi-rigid attachment member and an upper surface of the blade.

Abstract: An electrical assembly (10) comprising a first electrical device (12) comprised of a non-linear resistant, temperature responsive element (14) and first and second electrodes (16,18), the device (12) being connectable to a first power supply (20) such that a first electrical current (i.sub.1) travels through the resistive element (14) from the first electrode (16) to the second electrode (18). A second electrical circuit (24) is in electrical contact with the electrical device (12) such that the second circuit (24) may introduce a secondary electrical current (i.sub.2) into a localized portion of the non-linear resistant element (14), the second current (i.sub.2), when applied to the non-linear resistant element (14), causes the element (14) to change from a first resistant state to a second resistant state.

Abstract: A heater includes a first heat-generating conductor, a second heat-generating conductor and a shield conductor. The first heat-generating conductor and the second heat-generating conductor are integrally covered with the shield conductor. One end of the first heat-generating conductor and one end of the second heat-generating conductor are electrically connected to each other. When a current is applied from the other end of the first heat-generating conductor, the current flows in the first heat-generating conductor and the second heat-generating conductor in opposite directions. A negative potential -Vn is applied to the shield conductor from a negative potential generating circuit. A positive potential terminal connecting circuit is composed of two diodes. One of the diodes has its anode connected to the positive potential terminal of the negative potential generating circuit and its cathode connected to a first line.

Abstract: The present invention is a control system for controlling the temperature of the fusing system. This control system utilizes the knowledge of the heating characteristics of the fuser filament along with the knowledge that the human eye is most sensitive to temporal changes near the 8 Hz to 10 Hz rate as well as the concept of shape factors to control the rate at which power is applied to the filament to bring the fusing system up to operating temperature. From the study of the electrical characteristics of the heating element it is known that the heating element resistance in the fusing system under study exhibits a thermal time constant of 330 mS while heating. Also, from the summary of flicker regulations it is known that the best reduction in flicker is for the case in which a ramp voltage change is implemented with a ramp time of at least 1 second.

Abstract: A PTC planar heater according to the present invention is produced by bonding one or a plurality of PTC ceramic sheets, each having a pair of electrodes formed on the surface thereof, to an insulator. The electrode pairs are electrically connected in parallel by lead wires. An insulating elastic layer covers the electrodes to prevent warpage, electrical leaks, and shorting. A thickness of the PTC ceramic sheets equal to or greater than 0.5 mm prevents warpage. Resistance is adjusted by cutting conductive paths in the electrodes or by connecting predetermined portions of the electrodes. Further, in a PTC planar unit according to the present invention, a PTC thermistor element having a pair of electrodes formed thereon is in direct contact with one side of an insulation substrate, and a insulation substrate is mounted to the other side thereof.

Abstract: A plurality of supporting columns extend downwardly from a top wall of a cover attached to the electrical junction box body. A case surrounding the PTC element has projecting bars extending in the cover attaching direction. Each of the supporting columns has a guide groove receives the associated projecting bar so as to hold the case. The PTC element joints to connecting terminal strips having a heat radiation face. Further, the connecting terminal strip has a saw-tooth face at each side end thereof.

Abstract: The modular multizone heater system is for controllably heating areas of a structure, for example for bonded doubler reparation. The system comprises a number of heater cells to be placed in thermal contact with the areas to be heated of the structure. Each heater cell has a heating element and a temperature sensor. The heating elements of the heater cells are connected to a heater power supply to receive electric power. The heater power supply is controlled by a control unit receiving control data from a computer. The temperature sensors of the heater cells are connected to the control unit that relays the temperature data produced by the temperature sensors to the computer for monitoring, processing and control purposes.

Abstract: A new linear power control topology coupled with simple control techniques are presented which virtually eliminate the flicker problem as well as providing excellent power quality over a wide range of power levels. A modified one dimensional LMS control system similar to the standard LMS algorithm with multiple operating points and gain scheduling is also described which when combined with the new power control topology yield a dramatic reduction in flicker while yielding a universal voltage interface for world wide use.

Abstract: The temperature of a heated roller (1) is monitored by a heat sensor (19) which rests on metal rectangle (25) on polyimide strip (5). The top end of the strip is attached directly to the frame (3). the bottom end of the strip has a hole (7), which receives an arm (9a) of pivoted member (9). A coil spring (13) pivots member 9 to cause arm 9a to pull the strip into contact with the heated roller. Because of the wide contact and low force between the strip and the roller, wear is reduced and smooth operation is realized.

Abstract: A safety-assuring control device for an electric blanket which includes a PTC heater includes an integrated circuit microcontroller unit having first and second safety circuit inputs and an output connected to a control input of an electrically controlled heater switch. A neon tube is connected between the primary safety link return conductor of the heater and the first safety circuit input, to indicate whether there is a first type of fault in the PTC heater. A connection between the second safety circuit input and the secondary safety link return conductor of the PTC heater is provided which indicates whether there is a second type of fault in the heater. The microcontroller unit includes a preliminary fault detection circuit for supplying a limited power test signal in a test mode to the heater for a predetermined period of time prior to a full power operation of the heater.

Abstract: A sheathed heater comprises a heater disposed in a sheath tube by way of an insulation powder and is connected in series with a heat resistor and a current regulation resistor. The current regulation resistor is made from a cobalt-copper alloy which contains a copper component in the range from 1.0% to 14% by weight.

Abstract: A steamer for a steamable hair curler includes thermally isolated cold and hot water reservoirs. Water in the hot water reservoir is heated by a PTC heater. The volumetric capacity of the hot water reservoir is very small. The PTC heater has an intrinsic cutoff temperature high enough to boil water in the hot water reservoir and low enough to prevent deterioration of any component parts of the steamer, even in the absence of water in the hot water reservoir. Due to the thermal isolation of the reservoirs, water in the cold water reservoir is not substantially heated during normal operation of the steamer.

Abstract: The present invention is a heated wiper blade comprising an elongated blade and a heating element connected to the electrical system of a vehicle. The heating element utilizes a material with a positive temperature coefficient of resistance placed between a pair of conductive members. The conductive members span the length of the heating element to provide a uniform distribution of heat through the length of the blade. Electrical connections to the heating element are preferably located at one end of the blade. The heating element can be located inside the blade or between a semi-rigid attachment member and an upper surface of the blade.

Abstract: A heater on-time computing unit, provided in a heater control device, has a first fuzzy neural network for computing a heater on-time in accordance with a surface temperature of a heat fixing roller and a surface temperature change obtained from surface temperatures. A roller surface temperature predicting unit has the second fuzzy neural network for computing a predicted temperature of the heater in accordance with a surface temperature, a surface temperature change obtained from surface temperatures, and a heater on-time computed by the heater on-time computing unit. Thereby only roughly setting of parameters is required because the parameters are adjusted by sequential learning so that the optimal heater on-time is obtained. Therefore, the programming is simplified and it is possible to comply with differences in such as models, individuals, deterioration due to aging, and changes in environments.

Abstract: In an electric furnace including a heating device which includes a cooling water passage for cooling the heating device to prevent the heating device from melting, estimation of a molten metal temperature in the electric furnace using a heat equilibrium model is conducted taking into account a thermal loss by the cooling water, i.e., the amount of a heat taken away by the cooling water. Further, the amount of the cooling water flowing through the heating device is adjusted so that the thermal loss by the cooling water is in a predetermined optimum thermal loss range.

Abstract: A power control device is to be used with a pressing iron which includes a soleplate, a housing mounted on the soleplate and provided with a handle, a heating device disposed in the housing and operable so as to heat the soleplate, and a power supplying unit for supplying electric power to the heating device. The power control device includes a switch circuit adapted to connect electrically the heating device and the power supplying unit, an optical sensor unit adapted to be mounted on the handle of the housing, the optical sensor unit generating a first control signal when the handle is released and a second control signal when the handle is gripped, and a timer circuit connected electrically to the switch circuit and the optical sensor unit.

Abstract: A temperature sensing system that includes a temperature probe, a signal conditioning circuit, and a microprocessor. The conditioning circuit incorporates a novel dual voltage range measurement technique that improves the accuracy of such systems. The safety circuitry is provided in order to protect against thermal runaway and to inhibit or enable a door lock.

Abstract: A current control circuit for improved power application and control of thermoelectric devices to maintain the temperature of thermoelectric devices at a set point. The circuit includes at least one thermoelectric device, an inductor device, a current sensor and a switch device operatively connected in a series connection across a pair of terminals to allow current to flow therethrough when the switch device is activated to the "on" condition; a temperature sensor operatively positioned to monitor the temperature associated with the at least one thermoelectric device; a comparator device receives an input from the current sensor and provides an output to the switch device; a programmable control device receives an input from the temperature sensor and provides an output to the comparator device, the value of the output is determined by the difference between the sensed temperature of the at least one thermoelectric device and the desired set point temperature of the at least one thermoelectric device.

Abstract: A heater controlling unit used in a heat fusing device of an image forming apparatus, such as a copying machine, comprises a temperature detecting unit for outputting a detected temperature, a temperature change rate computing unit for computing the surface temperature of a heat fusing roller using the output of the temperature detecting unit, and an on-time computing and controlling unit for computing a heater on-time within a predetermined period by means of a fuzzy neural network using the above temperature and a temperature change rate found by the temperature-change rate computing unit, a heater controlling circuit for controlling the on/off action of the heater, a predictive computing unit for predicting the surface temperature, and a comparing and adjusting unit for comparing the actual temperature with the predicted temperature, and, when the difference is greater than a predetermined value (e.g., .+-.5.degree. C.), for adjusting the weights of the links within the network.

Abstract: The present invention relates to a temperature control method for a fixing device of an image forming apparatus using an electrostatic photographing process, and it is an object of the present invention particularly to realize excellent temperature control performance without any addition of any complicated mechanism or device to a fixing device using a heater having a small heat capacity.The present invention is characterized by:(1) Correcting a detected temperature, above all, correcting a delay in the detection by a temperature sensor, in accordance with a predetermined equation with a view to determining the electric power to be supplied (i.e.

Abstract: A modification circuit (30) is thermally coupled to and electrically isolated from a circuit element (20) of a utilization circuit (10). During modification, current pulses are passed through an isolation circuit (40) to the modification circuit which heats the circuit element, e.g., a resistor, of the utilization circuit substantially above the normal operating temperature range of the element, thereby modifying the electrical characteristics of the resistor and therefore those of the utilization circuit to which it is connected. During normal operation of the utilization circuit the circuit element of the utilization circuit is electrically isolated from the modification circuit.

Abstract: A Control circuit for a differential scanning calorimeter which includes a sample heater, a reference heater, a system for generating a sample heater DC voltage and a system for generating a reference heater DC voltage. A balanced operational amplifier arrangement is provided which includes a circuit for controlling the differential heater voltage and a circuit for independently controlling the average heater voltage, so that the average heater power and the differential heater power are independently controlled.

Abstract: In a toaster, a system is constructed to vary the duration of the toasting cycle. An RC network provides an oscillating signal to a counter, which upon the required number of oscillations being counted, triggers a transistor switch. The switch energizes the main solenoid switch which in turn deactivates the heating elements of the toaster. The RC network of the system comprises a variable resistor which may be manually operated, a heat sensitive resistor, and a light sensitive resistor.