Abstract: The present invention relates to a door-lock system (S) for a household appliance, in which said household appliance is of the type comprising a frame and a door hinged to said frame, and in which said lock-door system (S) comprises: an engaging member (2), which can be fixed to said door of said household appliance, and comprising a prong (22) and a security member (23) arranged substantially parallel to said prong (22); and a door lock device (1). The present invention also relates to an oven.

Abstract: A method and an assembly device for automated determination of a drilling position of a drill hole for a fastener for fastening a component to a possible wall area of a wall, wherein the method steps include: determining a surface contour of the wall area; examining the surface contour and detecting first irregularities in the surface contour using a first detection rule; determining a primary possible support surface area and a primary possible drilling position area that do not have any of the detected first irregularities; examining the surface contour of the primary possible drilling position area and detecting second irregularities in the surface contour using a second detection rule; and determining the drilling position inside the primary possible drilling position area such that the surface contour at the drilling position does not have any of the detected second irregularities.

Abstract: A door for a dishwasher appliance is provided herein. The dishwasher door may include an internal panel, an external panel, and a light source. The internal panel may define an inner face and an outer face. The internal panel may define a light channel from the inner face to the outer face. The external panel may extend across the internal panel in front of the light channel. The external panel may define an inner face directed toward the outer face of the planner internal panel. The light source may be positioned behind the internal panel. The light source may be directed at the light channel.

Abstract: A microwave oven includes a housing, which surrounds an oven space and has a flange configured to delimit a loading opening for the oven space. A door closes off the oven space and is disposed movably on the housing. Disposed on the door is a microwave shield, which is disposed at a distance in front of the flange, when the door is closed and is adjusted by an adjustment facility such that a position of the microwave shield can be set in three spatial directions relative to the flange.

Abstract: The present application in particular is directed to an oven muffle (1) comprising a lighting system (3). The lighting system (3) comprises a light source (6) and a light guide (4) attached to the outer surface of the oven muffle (1), the light guide (4) has at least one light guiding tube (4) arranged and adapted to couple light of the light source (6) into the light guiding tube (4), wherein the light guiding tube (4) extends in parallel to the light guiding direction along a respective wall (5) from a light tube exit window to its light tube face side, preferably lying beyond a respective edge of the wall (5).

Abstract: An attachment structure of a storage unit having: a tank casing body; a tank casing door member, and a lock portion; and an operation member, and a push button, wherein: an outer circumference of a storage unit is surrounded with an opening portion of an exterior panel; the push button is protruded from an outer surface of the exterior panel in a mount position of the exterior panel when the exterior panel is in assembling work; and a space for inserting a circumferential edge of the opening portion of the exterior panel is formed on the back of the push button.

Abstract: A heating apparatus includes an inverter power supply for driving the high frequency generating device, a holding member for holding the inverter power supply and cooling fan for cooling down the inverter power supply. The holding member is provided with a holding portion for holding the inverter power supply and an air guide portion for guiding cooling air from the cooling fan toward the inverter power supply, and the air guide portion covers the inverter power supply and guides the cooling air in a manner that a semiconductor switching device and a high voltage transformer of the inverter power supply are primarily cooled down.

Abstract: A safety apparatus for an output level-adjustable microwave oven includes a fuse disposed in a power supply line that connects a high power relay or a low power relay with a primary coil of a high voltage transformer of the microwave oven. Where a wrong operation occurs due to defects in the relays, such as a melting of any one of the relays, the fuse disposed in the power supply line connected to the primary coil of the high voltage transformer is cut off. Accordingly, a potential fire resulting from the wrong operation is prevented.

Abstract: A microwave oven for a vehicle includes an elastic vibration damping unit, and a joint unit which joins a body of the microwave oven to a vehicle through the vibration damping unit. The joint unit fixes the body of the microwave oven to the vehicle while the vibration damping unit damps vibration and impact generated from the vehicle in motion. Accordingly, inner devices of the microwave oven are prevented from being damaged by the vibration and impact.

Abstract: In a power-supply unit for a microwave tube, voltage between a helix power supply terminal and a cathode power supply terminal is divided into voltage slightly lower than the voltage of a collector power supply terminal. Uni-directional conductive means is provided between a voltage dividing point and the collector power supply terminal, and when the voltage of the collector power supply terminal is about to be lower than voltage at the voltage dividing point while the voltage approximates the voltage of the cathode power supply terminal, the uni-directional conductive means conducts and clamps the voltage of the collector power supply terminal so that the voltage is substantially equal to the voltage at the voltage dividing point.

Abstract: In the power supply control circuit, interposed between the power lines 1a and 1b is a serial circuit 21 constructed by connecting in series a radio interference suppression capacitor 2 for suppressing radio interference and a power supply holding switch 4. A node of the radio interference suppression capacitor 2 and the power supply holding switch 4 is connected via an auxiliary power line 1d to a primary side terminal 7a of a stepdown transformer 7, and another primary side terminal 7b of the stepdown transformer 7 is connected to a power line 1b. With the power supply control circuit, reduction of electric power consumption can be realized using a power supply holding switch with a small capacity.

Abstract: A microwave oven with an apparatus for detecting life time of components detects a frequency of opening and closing of a door switch even when AC power supply is cut-off, and detects a driving time of a high voltage transformer or a magneton according to their driving status, and accumulates and stores the detected driving time in a memory. The microwave oven includes a high frequency generation detecting portion connected to a high frequency generating portion for detecting driving status of high frequency generating components such as the high voltage transformer or the magnetron, and a door opening/closing detecting portion for detecting opening and closing of the door. A microcomputer counts the driving time of We high frequency components and the frequency of door opening and closing, and accumulates and stores the counted result in the memory.

Abstract: Timing of zero voltage in zero-voltage detector for detecting zero voltage of a commercial power supply 1 is predicted and input from the zero-voltage detector 6 is received only for a given time before and after the predicted timing, whereby overvoltage and overcurrent caused by a zero point shift can be prevented. Thus, it is provided a magnetron drive power supply which is excellent in stability for change in the power supply environment such as noise or instantaneous power interruption.

Abstract: A high-frequency heating apparatus is designed to maximize the input current while securing a uniform margin relative to the cutoff current, thereby enabling maximized and efficient output of high-frequency waves. The high-frequency heating apparatus includes: a power supply unit; an input current detector; a power converting unit for converting the power from the power supply unit into high-frequency waves; an inverter controller for controlling a semiconductor device; a magnetron for radiating electromagnetic waves; and a circuit for implementing negative feedback control, in the inverter control circuit, of the output from the input current detector. The apparatus further includes a control circuit having a microcomputer for outputting signals to the inverter controller so as to control the input current such that the input current characteristic of the high-frequency heating apparatus will approximate the current cutoff characteristic of the overcurrent circuit breaker with respect to the elapsed time.

Abstract: A normal position detecting mechanism for detecting a position of a functional component in a heating apparatus includes a drive member mounted on the functional component, a drive unit assembly mounted on the heating apparatus, and a switch for generating a detection signal. The driven unit assembly includes a switch actuating member, a bracket for supporting the switch actuating member, and a biasing member arranged between the mounting bracket and the switch. The biasing member applies a bias force for driving the switch actuating member against the direction for generating the detection signal. The drive member is positioned facing the switch actuating member when the functional component is in its normal position so that the drive member provides a force to move the switch against the biasing force to generate a detection signal.

Abstract: When power supply to a high voltage transformer starts, the phase &thgr; of the voltage of an AC power source when power supply to the high voltage transformer is stopped last time is referred to. In accordance with the value of the phase &thgr;, the phase of the voltage of the AC power source when power supply to the high voltage transformer starts is determined, so that the peak value of the rush current in the high voltage transformer is minimized.

Abstract: A microwave oven includes a power supplying part, a cooking chamber, a door of the cooking chamber, a magnetron, and high and low voltage generating parts supplying voltage to the magnetron, further including: a door switch installed on branch lines of a power line toward the high and low voltage generating parts, operating depending on opening and closing the door and selectively connecting the power supplying part with the high and low voltage generating parts; a power saving switch controlling a connection between the power supplying part and the low voltage generating part; and a controller switching off the power saving switch when a predetermined time elapses after the magnetron stops operating. With this configuration, in the microwave oven, a power saving function can be automatically selected, and automatically suspended when the door is opened.

Abstract: Disclosed is a microwave oven comprising a power supplying part, a cooking chamber, a door of the cooking chamber, a magnetron, and high and low voltage generating parts supplying voltage to the magnetron, further comprising a door switch installed on a branch line of power line toward the high and low voltage generating parts, operating depending on opening and closing the door and selectively connecting the power supplying part with the high and low voltage generating parts; a power saving switch controlling a connection between the power supplying part and the low voltage generating part; and a controller switching off the power saving switch when a predetermined time elapses after the magnetron stops operating. With this configuration, in the microwave oven, a power saving function can be automatically selected, and automatically suspended when the door is opened.

Abstract: The apparatus for etching a thin film using the plasma includes a reaction chamber having a diffusion area and a reaction area; an upper electrode disposed in the top of the reaction area; a lower electrode spaced apart from the upper electrode and arranged at the bottom of the reaction area; a RF power supply applying RF power to the upper and lower electrodes so as to form the plasmas between the upper and lower electrodes; a gas inlet applying processing gases to the diffusion area; gas-exhausting members sucking the residual plasmas and byproducts of the plasma etch; a buffer plate surrounding the lower electrode at the bottom of the reaction chamber and having a plurality of vent holes and vent hole protectors; and a shielding member between the lower electrode and the buffer plate, the shielding plate protecting the lower electrode from the plasmas.

Abstract: A microwave oven includes a main casing with a cooking chamber, a door for opening and closing the cooking chamber, and a magnetron in the main casing, for heating food within the cooking chamber. The microwave oven further includes a power supply part, a first door switch closed while the door is closed to supply electric power from the power supply part into the magnetron, a monitor switch connected in series to the first door switch, being operated in reverse relative to the opening and closing of the first door switch, and a control part determining that the first door switch is in trouble where the first door switch and the monitor switch are not operated in reverse to each other, and preventing the electric power from being supplied into the magnetron when the door is opened while the first door switch and the monitor switch are both closed.

Abstract: A high frequency heating apparatus including a circuit for driving a magnetron. A circuit comprises a leakage transformer, a second capacitor connected in series to primary coil of said leakage transformer, a second switching device connected in parallel with a series circuit of said primary coil and second capacitor, a first capacitor connected in parallel with said second switching device, and a first switching device connected in series to said second switching device. Under a structure of the present invention, the switching device and the leakage transformer, both being the key components of the circuit, may respectively be used in common either on a circuit of 200V-240V commercial power supply or on a circuit of 100V-120V commercial power supply. This enables volume production of the key components, which leads to a benefit of reduced cost of the components as well as the cost of heating apparatus.

Abstract: When power supply to a high voltage transformer starts, the phase &thgr; of the voltage of an AC power source when power supply to the high voltage transformer is stopped last time is referred to. In accordance with the value of the phase &thgr;, the phase of the voltage of the AC power source when power supply to the high voltage transformer starts is determined, so that the peak value of the rush current in the high voltage transformer is minimized.

Abstract: A microwave oven comprises a main casing with a cooking chamber, a door for opening and closing the cooking chamber, and a magnetron in the main casing, for heating food within the cooking chamber. The microwave oven further comprises a power supply part, a first door switch closed while the door is closed to supply electric power from the power supply part into the magnetron, a monitor switch connected in series to the first door switch, being operated in reverse relative to the opening and closing of the first door switch, and a control part determining that the first door switch is in trouble where the first door switch and the monitor switch are not operated in reverse to each other, and preventing the electric power from being supplied into the magnetron when the door is opened while the first door switch and the monitor switch are both closed.

Abstract: A microwave oven with an apparatus for detecting life time of components detects a frequency of opening and closing of a door switch even when AC power supply is cut-off, and detects a driving time of a high voltage transformer or a magneton according to their driving status, and accumulates and stores the detected driving time in a memory. The microwave oven includes a high frequency generation detecting portion connected to a high frequency generating portion for detecting driving status of high frequency generating components such as the high voltage transformer or the magnetron, and a door opening/closing detecting portion for detecting opening and closing of the door. A microcomputer counts the driving time of We high frequency components and the frequency of door opening and closing, and accumulates and stores the counted result in the memory.

Abstract: Disclosed is a normal position detecting mechanism of a functional component in a heating apparatus, comprising: a drive member mounted on the functional component side of the heating apparatus; a driven unit assembly mounted on a main body side of the heating apparatus; and a switch for generating a detection signal; said driven unit assembly comprising: a switch actuating member disposed in a back side of a flat wall surface of the main body side; a mounting bracket for operatively supporting the switch actuating member so as to be movable between the back side of the flat wall surface and the switch for generating the detection signal; and a bias member disposed between the mounting bracket and the switch actuating member, which applies a bias force for normally driving the switch actuating member against the switch for generating the detection signal; wherein the drive member is located in a position facing to the switch actuating member with the flat wall surface of the main body side sandwiched therebet

Abstract: A microwave oven comprises a main casing with a cooking chamber, a door for opening and closing the cooking chamber, and a magnetron in the main casing, for heating food within the cooking chamber. The microwave oven further comprises a power supply part; a plurality of contact parts provided to the main casing to be spaced from each other, being electrically connected to the power supply part; and a conductive part provided at the door, being electrically connected to the contact parts. With this configuration, the necessary components are decreased in number and the circuit is simplified in structure, thereby saving the cost of production and further improving the stability of the circuit.

Abstract: A method for controlling a cavity lamp of a microwave oven has a step of determining whether a door is opened. A cooking state is identified by determining whether a cooking key of a key input portion is selected when the door is opened. Whether the cooking cancellation key of the key input portion is selected when the door is not opened in the cooking state is identified. A cavity lamp is turned off when the cooking cancellation key is selected. Whether an open time of the door passes beyond an established predetermined time in advance is determined. The cavity lamp is turned off when the open time of the door passed beyond the predetermined time. Therefore, the cavity lamp which is turned on when a door is opened is turned off automatically or manually so that life of the cavity lamp is lengthened and loss of electric power is reduced.

Abstract: A high frequency heating device having a switching member screwed into a screw hole formed in a flange and fixed to the exterior. When the exterior is fixed to the body, a through-hole formed at that portion in the rear plate of the body through which the switching member passes is too large for the switching member. Thus, while the switching member is fixable to the exterior, the switching member cannot be fixed to the body onto which the exterior is not mounted. Therefore, a high frequency heating device can be provided, wherein an exterior switch more surely keeps the power supply circuit open when the exterior is removed.

Abstract: A power supply cut-off apparatus of a microwave oven includes a switch box, which is pivotally opened and closed, and provided at a prescribed position of an outer panel. A power supply connection unit is provided inside of the switch box and connected detachably to three power supply wires of an electric cord. A fuse is detachably provided in fuse fixing portions disposed on one side of the power supply connection unit.

Abstract: A microwave oven comprises a main body, a cooking chamber and an electrical component compartment. The electrical component compartment contains a fuse housing which is mounted on a bracket to hold a fuse. Plastic coupling members are integrally mounted onto the fuse housing bracket, into which a fuse is inserted. Each coupling member includes a guide projecting integrally upwardly from the bracket. Both sides of the fuse housing contact respective ones of the guides. A protruding portion on the top of each guide forms a cam surface for spreading the guides apart, and a stop surface for preventing upward dislodgement of the fuse housing.

Abstract: A microwave oven includes a power cord for supplying electrical power to electrical components of the oven. Wires of the cord are connected to a first set of terminals of a switch mounted on a main body of the oven. Electrical power is conducted from the first set of terminals to a second set of terminals of the switch by means of conductors carried by an outer panel of the oven that can be removed from the main body. The second set of terminals are connected to electrical components of the oven. When the outer panel is removed from the main body, the first set of terminals is disconnected from the second set of terminals, and an electrically insulative cover is spring biased to a position covering the sets of terminals.

Abstract: An oven assembly having a housing enclosing a cooking compartment and a blower compartment, and having a blower for circulating air within the cooking compartment, a door mounted to the housing, and a failsafe switch that is capable of deactivating the blower when the door is opened beyond a set point in the range between at least about 10% to 50%.

Abstract: A microwave oven includes a power cut-off safety switch which automatically cuts-off the supply of electric power to the oven if a housing panel is removed while the electric power supply cord is still plugged in. The switch is engaged by an extension of the housing panel which extends through a guide hole formed by another housing panel. The guide hole can have a non-planar shape to resist efforts to insert objects through the guide hole.

Abstract: The present invention relates to a ground structure of a printed circuit board in a microwave oven, where the microwave oven formed with a screw hole at a tip end of a bar extended from a body thereof and having a jumper wire connected to a ground pattern at around a screw hole formed at a printed circuit board while a bolt is screwed to a control panel through a screw hole formed at the tip end of the bar and through a screw hole formed at the printed circuit board are connected by the jumper wire, so that the printed circuit board is automatically connected and grounded to the body of the microwave oven when the printed circuit board is fastened to the control panel, thereby providing a convenience in assembly of the microwave oven and a stability thereto.

Abstract: A microwave oven includes a safety mechanism which automatically cuts off a supply of electric power to the oven when a panel of the oven housing has been removed, even if the power supply cord is still plugged in. The safety mechanism includes a switch disposed on the housing for cutting off the power. A cover for the switch is movable between a first position covering the switch, and a second position exposing the switch. The switch is biased to a power-cut-off position and the cover is biased to the first position. A structure of the panel is arranged to automatically move the cover to its second position, as well as to move the switch to a power-supply position, in response to the panel being in an assembled state. When the panel is removed, the switch automatically cuts off the electric power, and the cover moves to the first position covering the switch.

Abstract: A microwave oven includes an electric power supply shut-off mechanism for cutting off the supply of electric power when the housing is disassembled for repair while an electric power cord remains plugged into an electric outlet. A sensor in the form of a light sensitive semiconductor and/or a piezoelectric crystal senses when panels of the oven housing are removed and thereupon causes a controller to actuate a solenoid which deactivates a safety switch for cutting off the supply of electric current.

Abstract: A microwave oven includes a housing formed by relatively separable first and second panels. Electric switches are mounted on the first panel and are connected to respective wires of the power cord by the oven. Each switch includes a movable contact which moves away from a respective fixed contact when the panels are separated from one another, in order to automatically cut off the supply of electric power to the oven in the event that the worker forgets to unplug the power cord. When the panels are reconnected, the switches are automatically closed. Such automatic closing can be caused by magnetic force produced by magnets carried by the second panel. Alternatively, the automatic closing can be caused by screws carried by the second housing and which physically push respective movable contacts against their associated fixed contacts.

Abstract: A microwave oven includes a case forming a cooking chamber, and an outer panel mounted to the case. The outer panel is to be separated from the case when performing certain maintenance or repairs. Electrical terminals are mounted on the case and outer panel to perform the function of automatically disconnecting power to the oven in response to removal of the outer panel. A first arrangement of terminals can be provided for performing that function in the event of a removal of the outer panel in an upward direction. A second arrangement of terminals can be provided for performing that function in the event of a removal of the outer panel in a rearward direction.

Abstract: In a device (1) for the treatment of materials under the action of heat, and if appropriate also pressure, in a heating chamber consisting of a housing (2), containing the heating chamber, having a charging opening for the heating chamber which can be selectively opened or closed by means of a door (4), and a heating device (6), in particular a microwave heating device, for the heating chamber (7), the door (4) is so mounted that when a particular pressure in the heating chamber is exceeded it lifts off from the door frame (2) and is movable into a relief-opening position, out of which position it is moveable back into the original-closed position--after reduction of pressure--either automatically or by the application of force.

Abstract: An improved controller for a microwave oven capable of preventing it from an undesired heating caused by an erroneous operation thereof, which includes a heating member for generating heating energy; a power switch for controlling electric power supply to the heating member; a switch module including a plurality of switches for selecting a desired function; a microcomputer for outputting scanning signals having predetermined time differences to the switch module and for outputting a predetermined control signal in accordance with a key input signal outputted from the switch module; and a controller for controlling the power switch in accordance with control signals outputted from the microcomputer and a signal applied from the switch module, wherein the control signals includes a latch signal maintaining a predetermined state after the output signal of a switch is detected, while having the same level as a scanning signal outputted from a switch which is selected by an operation mode corresponding to scanning

Abstract: A new variable password safety interlock system for microwave ovens and other computerized or electrical appliance allows the user to dynamically and automatically generate a new password immediately prior to each use. The variable password comprises some prearranged transposition or combination of numbers of digits that were already entered into the microwave control panel by the user. The user first enters digits representing the microwave time, the target food temperature, the microwave power level, the actual time of day on display or some other required combination of digits or microwave console buttons, and then presses the "Start" button. The new value of the variable password for that use of the microwave will be some prearranged transposition or combination of the digits, numbers or buttons that had just previously been pressed by the user and that appeared on the microwave control panel at the moment the user pressed the "Start" button.

Abstract: An electrical control scheme which permits operating power for a microwave oven and a second electrical appliance, such as a refrigerator, to be withdrawn from a single electrical outlet utilizes electrical contacts across which a voltage differential is generated when the oven is in operation and includes wiring connected between the second electrical appliance and the microwave oven. The included wiring conducts electrical power to the second electrical appliance from the power cord of the microwave oven, and the control system further includes a relay having a normally-closed switch.

Abstract: A microwave oven having a cavity and a door for closing off the cavity. The oven is fitted with a pressure actuated safety catch device which prevents opening of the door as a consequence of a sudden pressure increase in the cavity. The sudden pressure increase in the cavity is used to activate the safety catch device which catches the locking device of the door.

Abstract: To improve the safety of the interlocking switch circuit comprising a monitor switch, primary switch and secondary switch which are on/off by the opening and closing of the electronic range door in order to control the operation/nonoperation of the microwave generation device of the electronic range. The above switches are taken as relay contact points respectively, so as to be able to operate the on/off of each switch from outside. By this, the detection jig is decreased, the detection time period is also shortened and a cause of the safety decreases due to the increase of the efficiency removed. In addition, the switch which turns the on/off of the microwave generation device of the electronic range is adapted to increase the safety of the interlocking switch circuit by being arranged independently.

Abstract: System and method for interrupting the delivery of microwave power to a microwave cavity when a door to the cavity is opened and an interlock switch fails to operate. A switch actuated by movement of the door applies an overload current to an overload protector in the filament circuit of the generator which supplies microwave power to the cavity, thereby interrupting the filament current and shutting down the generator.

Abstract: The invention relates to a microwave oven which neither generates hot spots nor destroys a magnetron by shutting microwaves when there is no load to be heated. This microwave oven is constructed so that the impedances are matched when there is a load, and the impedances are unmatched when there is no load, by shifting the location of the opening of the cooking chamber from the center of the wave guide. When there is no load, as most of the microwaves are converted to standing waves and the pressing waves do not reach the cooking chamber, then it becomes possible to prevent dangers such as the abnormal irradiation of any part, the destruction of the chamber case owing to the occurrence of the heat spot, and the abnormal heat generation due to the leakage of the short waves.

Abstract: The present invention provides a method and system for performing a delay start regardless of the open/close state of the microwave oven door, where the present time Tp is continually counted after a warning signal telling a user to close the door is produced, even if the door is opened during the pre-cooking start time stage or the door is opened during the post-cooking time stage, whereby further cooking is interrupted after the warning signal is produced until the door is closed. Therefore, cooking can be started at a pre-determined time even if the door is opened during the execution of the delay start.

Abstract: A cooking apparatus for heating food to be served and capable of being operated with utmost simplicity without using and choosing various cooking-mode selection keys so as to achieve superb ease-of-operation. The cooking apparatus includes a cooking chamber for placing and storing food to be heated by the apparatus and a detector for detecting a state of a door attached to the cooking chamber, the door being freely openable and closable against an opening portion of the cooking chamber. An optical sensor, having a plurality of light emitting portions is disposed in a side of the cooking chamber and a plurality of light receiving portions are disposed counter to the light emitting portions. A drive unit is provided for driving the optical sensor and a judgement unit verifies and determines a cooking mode suitable for the food placed in the cooking chamber responsive to a signal from the optical sensor, where the drive unit is activated when the detector detects that the door is closed.

Abstract: A cooking appliance has several sensors to detect which attachment has been placed in a cooking compartment. When a door to the compartment is closed and a start switch is operated within ten seconds, the appliance automatically starts cooking in a mode determined by the attachment detected by the sensors. After the door has been closed for ten seconds, even though the start switch is operated by accident, the appliance will not start cooking.

Abstract: A method for controlling a power relay for actuating a magnetron of a microwave oven in which contacts thereof are closed at various points of time or phase of an AC sinusoidal waveform input thereto with an equal probability, thereby preventing a transfer of the contacts of the power relay. According to the present invention, a count number of a relay counter is incremented periodically upon application of power, until a start key signal is inputted. The count number of the relay counter is then incremented by 1 whenever the start key signal is inputted and the power relay is toggled from its off state to its on state. An interrupt number is incremented periodically as the count number of the relay counter whenever an internal or external interrupt routine is performed. When the count number of the relay counter and the interrupt number are the same, the contacts of the power relay are closed at a phase or a point of time corresponding to the same number, so as to actuate the magnetron.