Abstract: A composite load circuit for use within another circuit includes at least one amplifying transistor. The composite load circuit includes first and second transistors connected in parallel. Each load transistor has a gate that receives a common control voltage. Each load transistor also has a different turn-on threshold voltage. A resistor, connected in parallel with the load transistors, limits an effective impedance of the load transistors.

Abstract: A portable communication device with battery conservation capability is capable of sensing (223) its power source and suppressing a battery conservation circuit depending on an actual voltage determined (225) from an analog-to-digital converter. Two or more voltage ranges are defined (227) such that battery conservation is disabled when an external power source is operated in one of the predetermined voltage ranges.

Abstract: A communication circuit capable of accurately detecting the signal level of the transmitted signal without impairing interchangeability with respect to an existing communication circuit. The communication circuit includes a first arithmetic unit 110 and a second arithmetic unit 120. The first arithmetic unit 110 executes arithmetic operations ofK=R1/(R1+R2)V4=V3-K.times.V1where V1 is a voltage of a transmission signal on a receiving side 100, R1 is a transmission impedance on the receiving side 100, V2 is a voltage of the transmission signal on a transmitting side 200, R2 is a transmission impedance on the transmitting side 200 and V3 is a voltage of the transmission signal transmitted to the receiving side 100 via a control line CL interconnecting the transmitting side 200 and the receiving side 100. The second arithmetic unit 120 executes an arithmetic operation ofV5=2.times.

Abstract: A method and apparatus for sequencing the operation of electronic circuits based upon the level of the voltage provided by an external power supply. One or more power supply sequencer circuits may be interposed between an external power supply and one or more electronic circuits. The power supply sequencer circuits comprise a transistor having its high current node coupled to an external power supply, its controlling node coupled to a voltage sequencing means such as a diode and a resistor, wherein the resistor is in turn coupled to the external power supply and the diode is coupled to the ground potential. The transistor has its controlled high current node coupled through a power input node to the power input for the electronic circuit to condition the voltage received thereby. The power input node is in turn coupled through a second resistor to ground potential.

Abstract: The electronic switching device serves to control the connection of a load to a voltage source by a switch which is controlled in a first operating mode directly by a binary signal furnished by a signal processing circuit and in a second operating mode inverted. The switching device has three terminals, of which the first permanently remains connected to a first terminal of the voltage source and to a first terminal of the load, whilst of the other two switching device terminals the one is connected to the second terminal of the voltage source and the other to the second terminal of the load. The switching device is configured so that it can be changed over from the one operating mode into the other by interchanging the connections between these two other switching device terminals and the second terminals of the voltage source and of the load, respectively.

Abstract: A circuit arrangement for monitoring a control circuit, which has a driver transistor with an inductive load and a second transistor in a circuit branch parallel to the inductive load, includes an additional, external current measuring device. A switching element, in particular a transistor and an ohmic measuring resistor, is provided parallel to the driver transistor. At a test instant, the current flowing through the inductive load is diverted to the measuring device and induces a voltage at the measuring resistor which is indicative of the status of the control circuit.

Abstract: To protect a switching device having a possible open-circuit failure condition, an arrangement is featured in which a thyristor is connected in parallel with the main current-carrying terminals of the switching device to be protected. The thyristor is connected so that the forward current direction of the thyristor is the same as the normal current direction through the main terminals of the switching device. The arrangement provides for the thyristor to present an irreversible effective short-circuit when its normal parameter ratings are exceeded. The protection arrangement is particularly suitable for insulated-gate bipolar transistors (IGBT's) and preferably employs a pressure-packaged asymmetrical thyristor (ASCR) as the protection thyristor. The ASCR should be selected to withstand the normal (snubber-limited) dV/dt of the voltage across the switching device.

Abstract: A circuit configuration for triggering a field effect transistor with a source-side load has a capacitor which is connected on one hand through a load path of the field effect transistor to a supply voltage and on the other hand both to a first charging device and to a first controllable switching device. The first switching device is connected between the capacitor and a gate terminal of the field effect transistor. A second charging device acts through a second controllable switching device to charge a gate-to-source capacitor of the field effect transistor. A comparator monitors a voltage at the gate terminal of the field effect transistor and makes the first switching device conducting when a predetermined value is reached.

Abstract: n (an integer of two or more) resistors are serially connected between a first terminal to which a first voltage is applied and a second terminal to which a second voltage is applied. Gates of the (n+1) MOS transistors are connected to the corresponding one among the first terminal, the second terminal, and nodes between n resistors. The sources of the (n+1) MOS transistors provide (n+1) different output voltages.

Abstract: A solid state power switching circuit for alternating current loads, in which operating power for the circuit is diverted from the switched current during power stealing intervals self-synchronized with the alternating current waveform. During periods in which current to the load is commanded, a load current switch is maintained in a low impedance state except for the duration of a short power stealing interval each half-cycle of the supplied alternating current. Self-synchronization is achieved with a current detector which senses whether or not the magnitude of the current diverted during each power stealing interval exceeds a current threshold, and pulse generator logic which shifts the power stealing intervals in time relative to the alternating current waveform in response to the previously sensed current magnitude.

Abstract: A method and apparatus for protecting a DC-AC converter having a transformer. According to one embodiment, an oscillator generates a periodic signal having a frequency. A switch switches an input voltage across a first winding of the transformer in accordance with the periodic signal. A watchdog device disables the switch if the frequency falls below a threshold frequency.

Abstract: In an active plug-in circuit, a mode setting section sets either a plug-in mode or a regular mode, depending on the power source voltage of a package. When the plug-in mode is set, a power consumption controller maintains an electronic circuit built in the package in a low power consumption mode. After the power source voltage of the electronic circuit has been stabilized, the mode setting section sets the regular mode. The circuit reduces the variation of power source current to occur when a power source pin mounted on a package connector is connected to the corresponding terminal of a mother board connector and on the transition from the plug-in mode to the regular mode.

Abstract: An over discharge protection circuit for a rechargeable battery which prevents an over discharge of the battery in response to a current operating condition, even though the operational state of an electric/electronic apparatus is changed for the purpose of saving the power consumption. The over discharge protection circuit comprises a selector selecting a threshold voltage in response to the operating condition of the electric/electronic apparatus; a comparitor comparing the output terminal voltage of said battery with the threshold voltage selected by the selector; a switch opening or closing a power feed line along which the battery is powered; and a controller controlling the switch in response to the comparison result by the comparitor.

Abstract: Re-powering an electrical equipment after recovery of service interruption is prevented if the power switch of the electrical equipment stays in ON position. During a transit period of time just after recovery of service interruption, the detection voltage from a post-voltage detection circuit is set to exceed the detection voltage from a pre-voltage detection circuit. In this condition, a photo triac connected in series to the power switch is rendered non-conductive so that the electrical equipment will not be energized.

Abstract: A power supply control apparatus for controlling a power supply circuit for outputting voltages of at least two systems is constructed by a first power supply circuit for generating a first voltage and a second power supply circuit for generating a second voltage, a controller circuit which is driven by the first voltage, a disconnecting circuit for disconnecting the second voltage by the controller circuit in accordance with a predetermined condition, a power supply controller circuit for controlling the second power supply circuit on the basis of the second voltage, and a supplying circuit for supplying a signal indicative of a state in which the second voltage has been outputted to the power supply controller circuit when the second voltage is disconnected by the disconnecting circuit.

Abstract: The threshold voltage and on-resistance of a four-terminal power MOSFET switch are reduced by partially forward-biasing (to, for example, 0.5 V) the junction between the body and electrical source of the MOSFET. Preferably, as the MOSFET is switched on and off to control the current to a load, the body is switched synchronously with the gate so that the source-body junction is partially forward-biased (i.e., biased at a level that is insufficient to cause a forward current to flow through the junction) when the MOSFET switch is turned on and the body is shorted to the source when the MOSFET switch is turned off, thereby reducing the leakage current through the MOSFET in its off state. The body bias may be derived directly from the gate voltage or from a separate voltage supply line. A current-limiting device and a voltage clamp may be used to limit the body current and voltage, respectively.

Abstract: An amplifier controller (104) is described for operating from a single voltage power supply (105). A switch (103) is coupled between the amplifier (102) and the power supply (105). The controller (104) includes a power conditioning circuit (106) for generating doubled and tripled voltages and positive and negative voltages for operating the controller (104) and the amplifier (102). Internal voltage regulators (138, 142) control the magnitude of the generated voltages. The controller (104) further includes: (i) a circuit (172) for disabling the controller (104) and amplifier (102) in response to an idle signal presented thereto, (ii) a circuit (178) for energizing the switch in response to a turn-on signal (128) so that the amplifier (102) can amplify, and (iii) a circuit (176) for sensing the presence or absence of negative polarity (Vss) on a second lead (188) of the amplifier (102) and, if not present, disabling the switch (103) despite the presence of the turn-on signal.

Abstract: There is described method and apparatus to obtain synchronized switching of switchgear. A superposition of forces is used wherein the moving contacts of switchgear driven by a conventional operating mechanism has a secondary force, either opposing or aiding, superimposed upon the mechanism force under predetermined conditions to incrementally either slow down or speed up the moving contact. The computed secondary force is applied by a small servo-motor attached to the moving contact shaft. The energy of the secondary force is derived from a real time comparison of the measured position of the moving contact with its preprogrammed position in ROM at each predetermined point on the voltage or current waveform. From this comparison the required pulse energy is calculated and fed to the servo-motor which translates into the secondary force of appropriate duration thereby making the necessary incremental velocity correction.

Abstract: An electronic device, for example an irrigation controller, accumulates energy from a source of energy, for example from incident light, in order to progress, over time, from an inoperative un-powered to an operative powered condition in a positively controlled, graceful and orderly manner. The device so progresses to operability regardless that it should, from time to time and at times, be totally devoid of energy, and regardless that it may accrue energy only but exceedingly slowly over periods of days, weeks and longer. A power monitor circuit of the device is made from an electrical circuit technology that is reliably operative at a relatively low voltage level, typically from BICMOS technology, whereas other device electrical circuits are operative only at a relatively higher voltage level, and are typically made from CMOS technology.

Abstract: A multiplexor having a multiplexor control input terminal for selectively providing one of a plurality of conductor voltage levels to a conductor. The multiplexor includes a first switch, which is coupled to the conductor, for providing a first conductor voltage level to the conductor. A second switch is also included and coupled to the conductor for providing a second conductor voltage level to the conductor. To provide a selective discharge path for the conductor during switching, the multiplexor further includes a third switch coupled to the conductor. A discharge circuit is also provided and coupled to the conductor and the third switch for sensing the voltage level of the conductor to turn on the third switch as necessary at the early stage of switching among conductor voltage levels.

Abstract: A control relay circuit and method for controlling a relay having a coil, for use, in particular, in operation of a light fixture circuit having an HID lamp. The relay control circuit has an input for receiving a control voltage signal and a voltage storage element connected across the input. The voltage storage element develops a voltage level as a function of time in response to the control voltage signal. A thyristor circuit, a switching element and the coil of the relay form a series circuit that is connected in parallel to voltage storage element A switch controller is connected in parallel to the voltage storage element and is also connected to the switching element.

Abstract: A method is described in which load current present in a thyristor device may be detected by monitoring the characteristic voltage found on the gate of the thyristor. Load status information may be used in various ways such as, to turn off the output, to signal a load voltage, or to act as a lamp-fail reset on an aircraft passenger reading light.

Abstract: A power switching circuit includes a power switching NPN transistor (1) having its collector electrode coupled to a reference potential terminal (17) and its emitter electrode coupled to an output terminal (7). A driver circuit (5) is provided having an input coupled to a supply terminal (6) and a driving current output coupled to the base electrode of the power transistor (1). A PNP transistor(4) has its emitter electrode coupled to the output terminal(7), its base electrode coupled to a reference voltage terminal (9) for receiving, in operation, a voltage which is positive relative to the reference potential and its collector electrode coupled to the base electrode of an NPN transistor (2). The NPN transistor (2) has its collector electrode coupled to the collector electrode of the power transistor (1) and its emitter electrode coupled to the base electrode of the power transistor (1).

Abstract: The present invention provides a switching device incorporating a simple circuit capable of avoiding the flash-on of a transistor when a power supply is turned on and off thereby reducing the OFF delay time. The output circuit comprises a FET (145) having a drain and a source connected in series to a current line for supplying a current from a power supply (VD) to an output detector (load) (L), and a photocoupler (149) for applying a driving voltage across the gate and the source of the FET (145) according to the output of an internal circuit (151), a differentiation circuit comprising a capacitor (7) and resistors (5,9) is connected across the drain and the source of the FET (145), and second transistor (3) having a collector and an emitter connected to the gate and the soruce of the FET (145) is driven by a charging current for charging the capacitor (7).

Abstract: A frequency slider circuit for reducing power dissipation in the form of switching losses in a switching device when the switching device is near its desired maximum temperature limit is disclosed herein. The switching device controls an electric load, such as a motor. The frequency slider circuit samples a current of the switching device. The frequency slider circuit then uses a current transducer to convert the current to a signal level. The signal level is then processed by a model of the thermal response of the switching device. The output of the thermal model is compared to a reference signal, and if the output of the thermal model is greater than the reference signal, the switching frequency of the switching device will be lowered gradually to keep the power generated during the switching periods to be below a predetermined value. A minimum frequency clamping circuit is included to ensure that the switching frequency never drops below a minimum value, to ensure stable operation of the switching device.

Abstract: A fault tolerant isolation system providing fault tolerant electrical isolation between different components receiving power from separate power sources regardless of which of the power sources fails. One power source provides operating voltage to an isolation device, which is a transceiver, buffer, quick switch, etc. The other power source activates a transistor switch coupled to the output enable input of the isolation device, and a current limit device is provided between the output enable and power inputs of the isolation device. In this manner, failure of either power source disables the isolation device and therefore provides fault tolerant isolation between the devices on either side. In the preferred embodiment, the isolation device acts as a high impedance open switch if its power is removed thereby isolating the devices on either side.

Abstract: A mailing machine includes a digital printer for printing a postage indicia on a mail piece. The mailing machine including a controller for controlling the operations of the mailing machine and a printer transport for transporting the digital printer to a cleaning station when the printer is not in use. A sensor is positioned at the cleaning station for sensing the presents of the printer and generating an output to the mailing machine controller in response. The mailing machine power supply includes a main transformer and a plurality of secondary transformer in parallel electrical communication over first and second electrical lines. A single-pole-double-throw switch has its first input and output stage interposed between the first electrical line between the main transformer and one of the second transformers.

Abstract: A solar water pumping system for home use utilizing amorphous solar panels and circuitry for maintaining proper power to the system. Three reference voltages in combination with switching circuitry achieve this purpose by constantly monitoring input and output voltages and allowing a non-discontinuous switching between solar power and battery power.

Abstract: Method and apparatus for logic signal level translation to a semiconductor switch. The logic signal input is converted by a first circuit referenced to a first power supply level to a current source or sink gated on and off by the logic signal. The resulting current is coupled to the input of a second circuit referenced to a second power supply level to control complementary devices providing a switching signal for coupling to the semiconductor switch. The second circuit preferably includes circuitry for assuring that both complementary devices cannot be on at the same time.

Abstract: An output circuit in which both the signal type (i.e., current or voltage) as well as the signal level range (for example, 0 to 10 V, -10 V to +10 V) are based on user input parameters. The circuit is integrated in an application-specific integrated circuit (i.e., ASIC).

Abstract: A clamping circuit for clamping a circuit node during an initial circuit powerup interval includes a switching circuit and a switching control circuit. The switching circuit is an N-MOSFET with its drain and source terminals connected to circuit ground and the subject node sought to be clamped, respectively, and its gate terminal connected to the switching control circuit. The switching control circuit includes a number of N-MOSFETs which are interconnected in such a manner as to receive the power supply voltage and generate a switching signal which turns the switching circuit N-MOSFET on during an initial circuit powerup interval to clamp the subject node and then off after the power supply has reached a preselected minimum value. Upon initial circuit powerup, the switching control circuit self-triggers itself to turn the switching circuit on and clamp the subject node at ground potential.

Abstract: A MOSFET is used to protect a battery driven load against the effects of a reverse-connected battery. This invention is particularly suitable for use with loads, such as those commonly found in motor vehicles, which contain semiconductor devices that may be severely damaged by a reverse voltage. The source of the MOSFET is connected to the positive terminal of the battery, and a gate driver circuit is used to provide a gate to source voltage sufficient to turn the MOSFET on when the battery is properly connected. If the battery is connected in reverse, the gate driver turns the MOSFET off, and the intrinsic body-drain diode in the MOSFET prevents a reverse current flow through the load. In conjunction with the MOSFET, a sensing device sends out a warning signal which may be used, for example, to turn off a portion of the load if the output of the battery falls below a level necessary to maintain the MOSFET in a fully on condition.

Abstract: An autoselecting interface for selectively connecting an input aircraft power source to one of two outputs according to a sensed voltage of the input aircraft power source comprises a pair of input terminals for connection to aircraft power sources; first and second pairs of output terminals; a first voltage sensor connected to the input terminals for producing a first trigger output when an AC aircraft voltage is present at the input terminals; a second voltage sensor connected to the input terminals for producing a second trigger output when a DC aircraft voltage is present at the input terminals; a first switch responsive to the first trigger output for electrically connecting the pair of input terminals to the first pair of output terminals; a second switch responsive to the second trigger output for electrically connecting the pair of input terminals to the second pair of output terminals; and an override circuit for disabling the second voltage sensor from producing the second trigger output when an AC

Abstract: It is an object of the present invention to offer a headlamp cleaning device which is always capable of attaining a constant cleaning capacity by keeping the ejected quantity of the cleaning fluid constant for a single cleaning operation without any regard to the fluctuations in the voltage of the electric power in the power source.The headlamp cleaning device according to the present invention is provided with an electric power source voltage monitoring means which monitors the power source voltage as applied to a cleaning device motor. This device furnishes the power source voltage to the electric power supply time setting means. When a cleaning device switch 9 is turned ON, the electric power supply time setting means 10-2 sets the driving time T to a longer time period when the value of the electric power source voltage is low, but sets the driving time T to a shorter period when the value of the electric power source voltage is high.

Abstract: In a power feed path switching circuit via which first, second and third stations are coupled to each other in a normal state, a first unit senses a first current flowing in a first path connecting the first and second stations via a branching node and disconnects a second path connecting the third station and the branching node from the branching node when the first current is sensed. A second unit senses a second current flowing in the first path and gradually discharges the second path when the second current is sensed. A third unit senses a third current flowing in the first path and grounds the second path when the third current is sensed.

Abstract: Method and apparatus for releasing a workpiece, such as a semiconductor wafer, from an electrostatic chuck. A "dechucking" voltage is applied to the chuck electrode having the same polarity as was used to retain the workpiece, but having a different magnitude selected to minimize the electrostatic attractive force between the workpiece and the chuck. There is an optimum value for the dechucking voltage which minimizes this force. The optimum value can be determined empirically, or it can be determined by a method based on the value of the current pulse produced when the workpiece is first mounted on the chuck.

Abstract: A computer having a hard disk drive includes a battery voltage monitor which establishes a shut down condition of the computer if the supply voltage falls below a chosen level V.sub.L. Upon start up of the hard disk drive motor, current through the motor is limited so that supply voltage of the battery to a computer does not fall below level V.sub.1, which level is greater than the level V.sub.L. Additionally during start up, current in the motor is controlled so that voltage supplied by the battery to the computer does not rise above a threshold level V.sub.2 which is greater than V.sub.1.

Abstract: The apparatus includes first, second and third connectors, a control signal generator (5.11) and first and second switches (5.9, 5.10). The first and second connectors each have a signal input terminal, a signal output terminal and a control signal terminal. The third connector has a signal input terminal (5.7) and eventually a control signal terminal (5.8). The first and second switching means each have first (a), second (b) and third (c) terminals, the first terminal (a) of the first switches (5.9) being coupled to the signal output terminal (5.5) of the second connector, the second terminal (b) of the first switches (5.9) being coupled to the signal input terminal (5.1) of the first connector, the first terminal (a) of the second switching means (5.10) being coupled to the signal output terminal (5.2) of the first connector, the second terminal (b) of the second switching means (5.10) being coupled to the signal input terminal (5.4) of the second connector. The first and second switches (5.9, 5.

Abstract: A current driver has a short circuit protection circuit which monitors the magnitude of the current driver's output voltage. The protection circuit looks for the failure of the output voltage to either change to a prescribed non short-circuit representative value within a prescribed time window after the onset of a voltage transition at the input node, or to maintain that value as dictated by the input signal. If either of these conditions occurs, the protection circuit takes action to reduce the driver's output current to a relatively small `short circuit` current.

Abstract: A protecting apparatus protects an electronic device which is provided on a vehicle having a storage battery and a solar battery and which inputs output voltages of the storage battery and the solar battery to the electronic device. The protecting apparatus includes a voltage determining unit for determining whether or not the output voltage of the storage battery is normal, an interruption unit for interrupting a path from the solar battery to the electronic device, and a control unit for controlling the interruption unit and thereby interrupting the path when the voltage determination unit determines that the voltage of the storage battery is not normal.

Abstract: In a device for suppressing voltage drops in apparatuses which can be connected with a battery via at least two lines, one line serves to supply voltage permanently and the other line can be switched on or off via a switch. To prevent voltage drops which can occur on the permanent voltage supply side from negatively affecting the voltage supply to the apparatus, the permanent voltage supply is taken over by the other connected line via a circuit arrangement situated between the two lines when voltage drops occur while the switch is closed.

Abstract: A switching power source applicable to an electronic apparatus and capable of stabilizing an output voltage with a high transform efficiency even when an input voltage varies over a broad range. The output voltage is controlled at the primary circuit side of the power source. The base current is maintained constant with no regard to the input voltage.

Abstract: A multi-pole group-operated switch configuration is provided for electrical distribution circuits. The switch configuration includes integral arrangements for sensing circuit parameters and supplying power for a switch operator of the switch configuration. The switch configuration includes a plurality of switch-pole units. In accordance with desired characteristics and features, one or more of the switch-pole units includes an integral current-sensing device, an integral voltage-sensing device, or an integral combination voltage and current-sensing device. The voltage-sensing device also provides operating power to power a switch operator and charge the batteries of the switch configuration.

Abstract: A device connects an external electrical power supply source to an aircraft on the ground to temporarily replace its auxiliary power units. During the overlap period of the two switches used in the aircraft to achieve this transfer, an impedance, preferably a resistance much greater than the internal impedance of the external source is connected in series on the external line. As soon as switching to the external source has been completed, measurement of a sudden drop in the external voltage brings about closing of a static switch which short-circuits the resistance.

Abstract: Disclosed is an apparatus for controlling a solenoid switch connecting a power supply to a load. The apparatus constantly monitors the level of output voltage of the power supply, and accordingly controls the engagement or disengagement of the solenoid switch. Initially at the time the power switch is just turned on, the solenoid switch would not be engaged until the voltage has reached a predetermined level. After the solenoid switch is engaged and power is delivered to the load, the apparatus would disengage the solenoid switch when the voltage level of the power supply goes beyond an upper limit or below a bottom limit. Utilizing the apparatus, the power input to the load can be kept in a desired range.

Abstract: A digital-to-analog converter for operating in a low power condition includes a delta-sigma modulator (10) for converting an n-bit digital input signal to an m-bit digital output signal. The output signal is filtered with a switched-capacitor filter (12) and an active RC low-pass filter (18). A low power supply detect circuit receives two power supply input voltages, the low and the high power supplies, and outputs a control signal on a line (38) indicating a low power supply condition. The digital-to-analog converter includes an output stage (26) with the analog output thereof being connected to an analog output terminal (30). A switch (28) is provided for connecting the output stage to the analog output terminal (30) in normal operating mode. In a low power mode, the low power detect circuit (20) generates a control signal on line (38) in response to the power supply voltage falling below a predetermined threshold.

Abstract: A "Y" adapter for supplying power to a marine vessel from a dockside power center having two receptacles includes two three-pole plugs insertable into the receptacles, a third four-pole plug for connection to the wiring system of the vessel and a sensing and control unit for selectively switching paths between these plugs. All conductor lines are switchable to the third plug and between the input plugs by a voltage and phase sensing unit and contactor arrangement. Energization of one input plug while the other one is plugged into a receptacle is prevented and other dangerous voltage circumstances are also prevented.

Abstract: A branching unit for use in a submarine telecommunications cable system which employs electrical power feeding for repeaters/regenerators and in particular a system employing multiple branching units. The unit terminates three line cables (at 1, 2, 3) and a sea earth (at 4) and includes three high voltage element relays (A, A1; B, B1; C, C1) only one of which is energized at a time. When electrical power is supplied between any two line cables the third is isolated and connected to the sea earth. Short circuit or open circuit faults in one line cable may be isolated and connected to the sea earth, whilst allowing powering of the remaining fault free two line cables. The unit is polarity insensitive and symmetrical, cathodic protection being provided on all three lines (FIG. 1).

Abstract: The present off/on delay circuit operates within the power supply of a microcomputer system to interrupt transfer of regulated DC voltage to the system microcomputer and attachments in respect to indications of power disturbance and system switch status produced in the supply. Upon termination of such indications, this circuit selectively delays reappearance of regulated DC voltage to the level required for system operation so that whenever the microcomputer resets, the attachments must also reset; thereby preventing lockout impasses in the system rebooting process. The circuit operates in response to a plurality of DC voltage indications in the power supply, including at least an indication distinguishing the state of AC source power as either good or bad, and an indication distinguishing the state of a manually operable system power switch as either on or off.

Abstract: A solid state, static power supply control mechanism for coordinated transfer of a load from a preferred source of AC power to an alternate source of AC power should the level of power transmitted from the preferred source fall below a set, adjustable level and thereafter, upon re-establishment of the proper level of operating power of the preferred source, re-transfer of the load from the alternate source to the preferred source. A unique method of current interlock prevents the alternate power source from connecting to the load until the current from the preferred source is absolutely interrupted, with the same criteria required for re-transfer from the alternate to the preferred source of power. This mechanism and associated switching technique insures supply of power to the load regardless of the preferred power source failure mode and regardless of the phase relation of the preferred and alternate sources of power.