Abstract: Protective relay for use in an electrical power system having electrical conductors which are energizable with an AC voltage. The protective relay includes a circuit for sensing the AC voltage to produce an AC output that has zero crossings and a time period between zero crossings, a circuit for supplying an electrical signal representing a preselected pickup value of volts-per-Hertz for the relay, and a circuit responsive to the AC output and to the electrical signal for generating an electrical level as a function of both the time period and the pickup value and for producing an output signal for the relay when the AC output exceeds the electrical level. In this way, the output signal is produced when a volts-per-Hertz value of the AC voltage exceeds the preselected pickup value of volts-per-Hertz for the relay. Other protective relay apparatus and methods are also disclosed.

Abstract: The digital samples (An) representing the components in phase (X) and quadrature (Y) of data signals, are digitally integrated by the assembly comprised of multipliers (14 and 15) and an adder (16). The energy signal (Bn) which is obtained, is loaded into a register (17) so as to be provided with the energy signal obtained on the preceding sampling time. The value (Bs) of the energy signal from which the energy signal decrease rate exceeds a predetermiined value, is loaded into a register (21). Then a comparator (23) provides a binary 1 signal transmitted on the output line (25) as the energy drop signal when the value of the energy signal (Bn) has fallen below a predetermined fraction of the value (Bs) stored in register (21).

Abstract: A battery-powered mobile communications unit for reception and transmission of signals in which the continued transmitter operation, following activation, is controlled in response to accurate detection of battery deterioration. The battery voltage is monitored by a reset circuit to detect any voltage drop that exceeds a predetermined threshold and a command unit responds to the reset circuit to turn the transmitter off as long as the battery voltage is below threshold and to turn the transmitter on when the battery voltage rises above threshold. The duration of the voltage drop is also measured to determine if the drop is instantaneous, due to interferences or extended due to a battery deterioration. If extended, the command unit will not turn the transmitter on, even though the reset circuit indicates a rise in battery voltage above threshold.

Abstract: A system for feeding and controlling low intensity obstruction lights, involving low power drain especially in radio stations powered by solar cells includes:a sub-system which not only generates the energy necessary to feed the obstruction light, but also detects solar intensity;a control sub-system which delivers energy to the obstruction lights, triggered in correspondence to a light threshold, generates indicator signals on the operating state of the main on/off switch and the power circuit breaker and generates a lamp failure control for telemetering purposes and fault controls for the individual obstruction lights for local displaying purposes; and a low luminous intensity and low power drain lighting sub-system.

Abstract: A direct current power supply configuration for use in a wide variety of electronics applications, is described. The invention features high precision capability with relatively simple circuitry. A system of panel indicators eliminates the need for a panel voltmeter and improves serviceability and ease of operation over the prior art.

Abstract: A power voltage drop detecting circuit includes VDD and ground terminals supplied with power voltage VD, a resistor connected at one end to the VDD terminal, a MOS transistor connected between the other end of the resistor and the ground terminal, and a CMOS inverter for producing an output signal according to a voltage at the junction between the resistor and the MOS transistor. The detecting circuit further includes a control pad connected to the control gate of the n-channel MOS transistor and supplied with control voltage VC at different levels in the test mode and detect modes, respectively.

Abstract: An apparatus and method for detecting an AC power failure condition employs a fast attack, slow decay, energy storage circuit for tracking an AC input signal and for providing a slowly decaying output based upon a last received peak voltage input value. A current detection circuit monitors the current flow to the storage circuit from the AC mains and generates a current detection signal in response thereto. A power failure condition is declared when either the voltage across the energy storage circuit decays below a selected threshold value or current is not detected flowing to the energy storage circuit at a selected time. A particular current detection circuit employs a high permeability core which is saturated by a current in the sensed line having a current value below an expected peak current flowing to the energy storage circuit. An interrogation pulse periodically energizes an interrogation winding which, in the absence of current in the sensed line, induces a signal across an output winding.

Abstract: A voltage monitoring system for mounting on a test point in an AC power distribution system provides an output when the voltage level on a conductor is above a predetermined minimum level. Within a sensing unit mounted on the test point a rectifier circuit develops from a capacitive coupling to the monitored conductor a voltage dependent on the voltage level of the conductor. A potentiometer applies a portion of the voltage to the gate of a MOSFET transistor, which actuates a reed-contact relay to control external switching circuitry. The potentiometer is user-adjustable from the front of the sensing unit to enable the minimum threshold level to be set.

Abstract: A system for monitoring a battery voltage level and A.C. power supply. The A.C. power supply and a backup battery are used to power a voltage regulator which provides a reference voltage to the system. A first comparator circuit senses a drop of the voltage from the monitored battery below a predetermined level and provide a signal in response thereto. A second comparator circuit senses the loss of A.C. power and produces a signal in response thereto. A backup battery provides power to the system in the event of the loss of A.C. power. The signals produced by the comparator circuits activate a timer which in turn activates an alarm to indicate a problem in the system. The timer may be automatically deactivated by a return of the battery voltage level above the predetermined value to prevent false alarms. A second timer is also provided to provide deactivation of the alarm during servicing of the system. The system is designed so that the alarm will be sounded in the event of loss of A.C.

Abstract: A micropower DC voltage indicator is provided that is a two terminal device with a very high input impedance. An oscillator circuit is provided by a series of inverters, such as metal-oxide semiconductors (MOS) with the power inputs connected in parallel. A suitable RC circuit connects the output of one MOS inverter to the input of another MOS inverter, otherwise the output of each MOS inverter connects directly to the input of the next MOS inverter. Across one of the MOS inverters is connected a liquid crystal display which indicates if a DC voltage within a specific range is applied to the two terminals of the DC voltage indicator. The two terminal inputs to the oscillator circuit have a very high impedance and operate over a fairly broad DC voltage range.

Abstract: A supervisory device of a varying quantity measuring apparatus including a main scale and an index scale which are moved relative to each other in accordance with a physical varying quantity, a main power supply circuit which outputs a predetermined DC stabilized voltage by operating a power switch, and an encoder which is driven by the voltage output from the main power supply circuit and converts the relative movement of said both scales into electric signals to be displayed.

Abstract: An indicating system includes first and second voltage comparators, first and second output circuits which are respectively supplied with output signals of the first and second voltage comparators, and first and second indicating elements which are connected to a common output terminal of the first and second output circuits. A first input terminal of the first voltage comparator is supplied with a first reference voltage, and a second input terminal thereof is supplied with a control signal. A first input terminal of the second voltage comparator is supplied with a second reference voltage, and a second input terminal thereof supplied with the control signal. When the voltage level of the control signal is higher than the first reference voltage, the first output circuit causes a current of a first polarity to flow to the common output terminal. As a result, the first indicating element is lit up, and the second indicating element is not.

Abstract: Two different set voltages are respectively compared with a power source voltage. When the smaller set voltage which is close to a minimum operating voltage of an arithmetic circuit coincides with the power source voltage, a clock signal generator, and hence the arithmetic circuit are stopped. When the power source voltage increases to coincide with the larger set voltage after the clock signal generator is stopped, the clock signal generator and hence the arithmetic circuit are restarted.

Abstract: A device simply and effectively senses undesirably high temperatures in a refrigerated volume with an accuracy of about 3 percent, and activates an indicator in response to the sensing. A temperature probe is disposed in a freezer, refrigerator, or cooler volume, the probe including a negative temperature coefficient thermistor forming part of a voltage measurement bridge. The resistors of the voltage measurement bridge are all accurate to one percent, and are connected up to a voltage comparator of an integrated circuit. A 9 volt battery powers the device. The device also includes a low battery voltage sensor for activating the indicator when the battery voltage drops below about 8.2 volts, and a sensor for detecting when the probe is damaged or disconnected. The probe detection circuit includes a Darlington transistor, and resistor, the Darlington transistor being connected through a diode to the indicator. The indicator may include a piezo electric horn driven by a horn oscillator circuit.

Abstract: This invention relates to apparatus which can detect both interruptions and reductions in an alternating current input extremely quickly. This allows an orderly shut down of the equipment before the output of the equipment power supply decays. The device can be utilized in any application requiring detection of changes in an alternating current input.

Abstract: A system senses alternating current in a conductor, such as a main line supplying electrical power to a home, and responds to the sensed current as by providing a warning signal when the sensed current exceeds or is less than a preset value for a predetermined short period of time. The current sensor itself is a simple coil of wire, either with an air core or a partial ferromagnetic core, which can be easily operatively associated with the current carrying conductor without the need for disconnecting the conductor from its terminals and which when installed does not present the hazards associated with current transformers.

Abstract: A contact monitor and annunciator unit for providing a persistent warning in the event one of a selected number of event monitoring circuits associated with a mobile refrigeration system opens. The unit includes a number of warning circuits that are electrically isolated from the monitoring circuits by optical isolators and a separate power supply so that the initial cause of a shut down due to abnormal operating conditions can not only be annunicated but also differenciated from a shut down caused by a momentary power failure.

Abstract: A multiphase imbalance monitor utilizes a resistive summing network for sampling the ac voltage in each phase of the system under consideration. The summing network provides a zero voltage output under normal conditions. When a phase imbalance or missing phase condition occurs, the summing network provides a finite output voltage which can be used to actuate indicating and/or interrupting means.

Abstract: Apparatus for detecting, in advance, by a desired length of time, the imminent failure of electric output power provided by an electric power supply due to the reduction or loss of input power. The magnitude of the voltage on an energy storage reservoir capacitor is monitored for deriving a voltage signal proportional to the rate of change thereof. The rate of change voltage is multiplied by a voltage proportional to a desired early warning time interval and this product is added to a voltage proportional to a minimum value of voltage on the capacitor, thus representing an amount of stored energy sufficient to sustain normal output power for a desired time interval. The voltage derived by the adding means is compared with the voltage on the energy storage capacitor for signalling imminent power supply failure when the compared voltages are equal.

Abstract: A circuit arrangement detects and stores power line faults. The occurrence of sporadic faults as represented, for example, by inadmissibly long network collapses, which could lead to shut-down of a current supply and, therefore, to downtime of a computer are generally difficult to detect because the faults disappear given a return of the network, as does, therefore, the prerequisite for detecting the cause of such faults. For the purpose of detecting the cause of the fault, the rectified power line voltage is supplied to a comparison circuit followed by a signal circuit. The signal circuit is connected to a memory which influences a display. As a result, power line faults remain stored despite the return of the power line input voltage. The circuit arrangement is particularly suitable for use in power supply systems for data processing devices.

Abstract: A power failure protector circuit prevents spurious output signals from an electronic circuit when power to the electronic circuit is interrupted. The output of the electronic circuit is effectively blocked by a switch. The switch is turned off when the power supply is turned on and remains off until the power supply is interrupted. A capacitor is normally charged to the operating voltage of the power supply and when the power supply is interrupted, the capacitor discharges to turn the switch on during the interval when the operating voltages of the electronic circuit are decaying. The capacitor also provides a power source to maintain the operating voltages of the electronic circuit near normal for a short interval after the power supply is interrupted thus insuring correct operation of the electronic circuit until after the switch is turned on and the output from the circuit is blocked.

Abstract: An arrangement for storing user programmed system timing information in a microprogrammable system in the event of a power outage. The system includes a static random access memory (RAM) for periodically storing microprocessor-generated timing information and an electrically erasable programmable ROM (EEPROM) which is coupled to the static RAM for the temporary storage of this information in the event of a power outage. Also provided in the system is a power down sensor responsive to an AC-coupled power supply for detecting power loss to the system. When the input voltage drops below a predetermined value, the contents of the static RAM are automatically transferred to the nonvolatile EEPROM.

Abstract: A battery-powered, microcomputer controlled optical bar code reader automatically turns itself off under certain predetermined conditions, so as to prevent operation when the battery voltage is low, when the microcomputer of the circuitry controlled by the microcomputer is malfunctioning, or when the scanner has been turned on, but is not being used.

Abstract: An active transponder of an identification system comprises a memory for storing coded information and supplying it to a transmitter output, and data means independent of the memory for supplying further information to the output. The transponder has a battery and the data means can comprise detectors which detect when the voltage of the battery falls below respective predetermined levels. The data means can also comprise input connections arranged to receive signals representing the updated values of respective parameters. These signals are supplied to respective inputs of a data selector independently of the memory.

Abstract: A power supply particularly for use with a traffic control system has a voltage monitoring and control system which continually monitors the line voltage fed to the traffic control system and automatically turns off the power when the voltage drops below a predetermined minimum for a predetermined time period or provides a warning signal should the voltage drop below a higher second predetermined minimum for a predetermined time interval. In the event that the voltage returns to a predetermined acceptable value for a predetermined time period, the power is automatically restored and the warning signal discontinued. The monitoring system includes sensors operative in response to each of the control parameters which operate in conjunction with logical control circuitry to effect the desired controls.

Abstract: A multi-phase undervoltage detection circuit is disclosed wherein a multi-phase input voltage is compared to a reference. If the peak level of the input voltage is above the reference, a capacitor is discharged. If the voltage of any one of the phases is below the reference, the capacitor charges above the level of the input to a flip-flop. At the same time the voltage of another of the phases clocks the flip-flop. Since the input of the flip-flop is "high" when it is clocked, it changes states and its output goes "low" which provides a circuit output indicative of an undervoltage condition. If no undervoltage condition exists, the flip-flop will not change states and the circuit output is indicative of a non-undervoltage condition.

Abstract: To accurately check a battery of a camera, a battery checking operation must be performed under maximum load current, namely, the load current of a shutter release magnet or the like. The invention avoids the effect of a current through the magnet triggering a photographic operation of the camera during a battery check by having currents flow to a plurality of selected loads of the camera, such as light emitting diodes, etc., instead of through the magnet. The plurality of loads are preselected to draw the total sum of load currents nearly equal to the maximum load current. A battery check can be performed without applying a drive current to the largest load and yet the accuracy of the battery check thus obtained equals that of the accuracy obtainable with the largest load.

Abstract: A system responsive to the voltage of a motor vehicle battery when the vehicle engine is not running operates to disconnect the battery from the vehicle electrical loads prior to the point at which the battery becomes too discharged to restart the vehicle engine. The apparatus which operates to disconnect the battery from the loads is inhibited if an abrupt battery voltage drop indicative of vehicle entry is sensed, and the inhibit is maintained for a timed period sufficiently long in duration to allow entry of the vehicle and starting of the engine.

Abstract: A short range, low power, radio wave transmitter which acts as a miner locator. The transmitter is incorporated with the cap lamp circuitry for the miner. It utilizes the same self-contained power source and its wire connection thereto acts as the transmitter's antenna. No action on the miner's part is necessary in order to begin the transmission which may be on a specific identifying frequency for each miner. An electronic crowbar circuit may be used to conserve power for the transmitter by cutting off power to the cap lamp should the voltage across the self-contained power source fall below a preset level. This enables the transmitter to function for several days by reducing the load on the power source.

Abstract: A power outage indicator utilizes a smectic liquid crystal display cell, capable of storing information indefinitely, to provide a visual indication, of predetermined form, that power to a given installation has been interrupted. Prior to installation, the smectic liquid crystal display of the power outage indicator is heated and an appropriate voltage placed between the display electrodes to cause the liquid crystal material to align homeotropically, as the liquid crystal material cools to the smectic state; a clear stable texture results. Upon loss of power, stored charge, as in a storage capacitor, is enabled to flow through at least a portion of at least one of the display electrodes, reheating the liquid crystal material therebetween and, upon cooling without an applied field, converts a portion of the liquid crystal layer to a state having differing light-propagation properties than the remainder of the display.

Abstract: A transistor switching circuit is provided for providing an indication of when the level of an input signal has passed through a first threshold level, such indication continuing unless such input signal has returned beyond the first threshold level to a second threshold level. Such circuit is useful in indicating whether the battery of a battery powered device should be replaced taking into consideration small variations in the output of the battery after the initial replacement indication has been provided.

Abstract: A circuit for detecting a difference in the relative magnitudes of two voltages includes a current sensing circuit connected between the first voltage and ground to thereby cause a first current to flow in the current sensing circuit, an amplifier connected between the second voltage and ground and connected to the current sensing circuit to thereby cause a second current to flow, the second current being equal to the first current when the first voltage is equal to the second voltage, and a variable impedance inverter connected to the first voltage and connected to the amplifier, the variable impedance being controlled by the first voltage, the output of the inverter thereby being related to the difference between the first voltage and the second voltage. The invention is particularly useful for controlling a battery backup power supply in a microprocessor having a volatile memory and for creating precision delay circuits.

Abstract: In a microcomputer system arranged to operate with electrical power from a battery installed on a vehicle, the voltage of the power is detected to see whether it is below a predetermined value or not. When the voltage is below the predetermined value, a voltage detector produces an output signal which will be fed to a switching circuit formed by a D-type flip-flop. The D-type flip-flop is also responsive to a read instruction signal applied from the central processing unit of the microcomputer to a nonvolatile random access memory (RAM) thereof which is supplied with power from the battery all the time. With this arrangement, when voltage drop or sag is detected, the RAM is put in stand-by condition in which reading and writing operations are inhibited. In this stand-by condition of the RAM a central processing unit (CPU) of the microcomputer system is capable of operating as long as the power voltage is above the minimum operating voltage of the CPU.

Abstract: A warning device (10), typically situated in an illuminated exit warning sign, broadcasts voice commands generated by a synthetic speech synthesizer (U3) via speaker (SP1). A programmable microcomputer (U2) senses a loss of AC power and generates a user initiated voice command. Upon the detection of a fire or smoke condition, the microcomputer (U2) generates a priority warning. The device (10) includes a self-contained, charged power supply (12) that powers the microcomputer (U2) and the synthesizer (U3) in the event that the externally supplied AC power ceases. Constant illumination is provided by lamps (32) or (40). A user operated switch aids in programming the microcomputer to provide two sets of audible phrases.

Abstract: The rectified output voltage of the transformer of a d.c. to d.c. converter, as represented by a voltage divider output, is compared with a reference voltage in a voltage regulator (15), the output of which is compared in a comparator (29) with a sawtooth wave to produce a sequence of pulses the duration of which depends upon the output voltage of the regulator. These pulses are provided to the transformer through a driver circuit capable of operating at a very low input voltage. One flank of the square wave produced by a component of the sawtooth wave generator is differentiated by a capacitor (39) to provide transient pulses to the transformer to keep it operating in the event the input voltage to the converter exceeds the output voltage. Another comparator (59) is provided to shut down comparator operation when there is a short circuit at the output and also for a brief start-up interval during which capacitors are charged up.

Abstract: An electronic appliance provided with an output section to produce, as an output, input data introduced from an input section an operational result of the input data, and a power source section to supply electric power to the output section, wherein the appliance is further provided with a detection device for detecting abnormality in the output operation of the output section based on a decrease in the power supply from the power source section or an abnormality in the output operation of the output section based on the power decrease, thereby inhibiting data input from the input section when the decrease in the power or the abnormality is detected.

Abstract: A circuit for monitoring a d.c. voltage level and for generating a signal in the event the level falls below a fixed percentage of a desired level. The circuit utilizes a comparator, the inputs of which are fed by two leg resistive network the resistance values of which are in a ratio substantially equal to the percentage value. A capacitor is connected to the lower resistance value leg and to its input to the comparator. The output of the comparator is connected to one input of a second comparator the other input to which is connected to the capacitor. The output of the second comparator comprises the generated signal.

Abstract: A pulse for resetting computing equipment is generated upon a drop in the supply voltage. In a first embodiment of a circuit furnishing such a reset pulse, a comparator is used whose inverting input is connected to the supply line through a capacitor and to ground potential through a parallel diode-resistor combination. The direct input is connected to the tap of a voltage divider and is connected through a feedback resistor to the output. This circuit can detect drops in supply voltage in the order of the forward drop across the diode. Alternatively, a RC oscillator can be used to generate a reset pulse. If the capacitor in the circuit is not recharged in time by a pulse furnished by the computing equipment being controlled, it is assumed that failure to receive the pulse is indicative of a drop in supply voltage.

Abstract: Power supply sensing circuitry comprises a first comparator for determining whether the power supply potential voltage exceeds by a predetermined amount the voltage required to operate a data processing system connected to the power supply potential, and a second comparator for determining whether the power supply potential is at least the voltage required to operate the connected data processing system.

Abstract: A control system is employed to selectively inhibit false signal transmissions between a communications processor and a plurality of peripheral devices during transient power states. The control system includes a comparator which detects a decrease in the unregulated power supply voltage as compared to the regulated voltage to anticipate an impending loss in regulated voltage. In response to a detected drop in unregulated voltage, a transistor interrupts the power supply to communications lines. Simultaneously, the transistor interrupts the power supply to a light source of an optically coupled relay which is employed to actuate a peripheral such as a mailing machine. In order to assure that the communications processor will initiallize after a transitory drop and a recovery in line voltage, a processor reset signal is also generated by the control system as a function of a detected decrease in unregulated voltage.

Abstract: A circuit is provided for detecting a low power condition which is undesirable and effectively turns off a computer system to prevent incorrect operation thereof. The circuit does not turn on the computer system until the correct power condition is achieved. The circuit is also sensitive to the power condition to establish the time duration permissible for causing the computer system to be turned off.

Abstract: Apparatus for indicating the level of flowable material in a storage bin comprising a motor rotatably suspended by a spring within a protective enclosure and a drive shaft coupled by a ball-and-detent clutch to a paddle disposed within the bin to engage material therein. When the material reaches the level of the paddle, the drag on the paddle causes the motor to rotate within the enclosure and thereby to activate a switch disposed within the enclosure and coupled to the motor. A spring returns the motor to the switch-deactivated position when the material level decreases and the consequent drag is removed from the paddle. Electronic circuitry disposed within the housing includes field-selectable fail-safe circuitry for indicating either a high or a low material condition in the event of a power failure or the like independently of actual material level.

Abstract: A circuit (10) is provided for use in a telecommunications integrated circuit which has a memory for storing a telephone number. The circuit (10) essentially comprises a latch having differential nodes (22, 28). The circuit (10) serves to detect when the supply voltage provided between the supply terminals (12, 14) drops to a level which causes loss of the data stored in the integrated circuit memory. An output signal (PUC) is driven to a low state upon detection of loss of power. For a slow return of supply power the nodes (22, 28) are respectively pulled to low and high states by current leakage through diodes (30, 36, 38) connected to the power terminals (12, 14). For a rapid supply voltage transition the latch node (28) is pulled high by capacitive coupling through a diode (30). This serves to set the latch in the condition where the output node (22) is at a low state to indicate loss of power. After generation of the PUC signal in the low state, external circuitry provides a reset signal (.phi..sub.

Abstract: The smoke detector is powered by standard AC current and a stand-by power source consisting of rechargeable batteries. A detector is provided for detecting the loss or failure of AC power, and the shift to the stand-by power source. The power loss detector initiates a time delay after which the smoke detector signal alarm is energized to alert the user about the loss of AC power. If AC power is restored before the time delay interval, the signal is not energized since the user need not be alerted. If the alarm is energized to alert the user of a loss of AC power, a manual reset switch may be used to terminate the alarm. If the manual reset switch is not used, the alarm is terminated automatically upon the restoration of AC power.

Abstract: A sump pump detection and alarm system, comprising electrical circuits and components to detect the existence of three different conditions, namely (1) a high water condition with electric power still available, (2) a high water condition when electrical power has failed, and (3) a failure of electrical power to the sump pump even though there is no high water level at the time, and to energize an alarm when detected to indicate which of the three conditions exists. The invention includes remote alarm stations, and in addition connections to the on-premises telephone line to produce a busy signal or other signal when such number is dialed in the event one of the three sump pump conditions exists, plus connections to a radio transmitter to transmit a radio signal when one of the said conditions exist.

Abstract: A circuit apparatus including a circuit interrupter connected between an AC supply and electrical equipment to be protected and operational in a first condition to transmit power therebetween and operational in a second condition to interrupt power transmission therebetween, a control circuit for producing the first condition in response to normal supply voltage and for producing said second condition in response to abnormal supply voltage, a delay circuit connected to the control circuit and adapted to produce a minimum time delay between successive occurrences of the first condition, an overvoltage circuit adapted to produce the second condition in response to a voltage from the supply that exceeds a predetermined maximum level, and an undervoltage circuit adapted to produce the second condition in response to a voltage from the supply that is below a given threshold level.

Abstract: A reset generator circuit including a power monitor subcircuit which provides first and second logic level signals which specify the power supply as being above or below a preselected threshold level. A logic circuit comprising a series of interconnected NAND gates responds to the output signals generated by the power monitor subcircuit and to a signal from a capacitor charge monitor circuit. The capacitor charge monitor circuit develops logic signals which reflect the magnitude of the voltage across a capacitor which is part of a timing circuit. The control signal output from the logic circuit drives one input to a reset control gate and also controls the charge on the capacitor. The other input to the reset gate is also driven by the charge monitor circuit. The reset gate operates a switching element which provides the proper reset signal adapted for coupling to a microprocessor.

Abstract: A circuit for detecting power supply variations in which a first and second transistor are connected in a cross-coupled mode. A load device is connected to each transistor and to a source of power. The loads are unbalanced such that upon application of power to the circuit a first state is always assumed. The cell is forced to its second state. A charge transfer device is connected between first and second nodes formed at the connection between the first transistor and its load and the second transistor and its load. Upon reduction of power supply voltage below that of the active node, a charge transfer takes place which allows the cell to return to its initial state. Detection of the initial state indicates loss or reduction of power has occurred.

Abstract: A solid-state power controller in combination with a solid-state indication circuit is reminded for exhibiting OFF status using a depletion mode field effect transistor that permits an active signal to appear at its source and drain terminals when its gate, coupled to the power controller, is not energized. Such OFF indication circuitry is also combined with solid state ON indication circuitry using a device such as a bipolar transistor to exhibit an output when its base, coupled to the power controller, is supplied a signal.

Abstract: When the battery voltage is sufficient, and not nearing the point of insufficiency, a light-emitting diode is steadily illuminated. As the battery voltage decreases, the steady component of illumination decreases and also, when the decrease has proceeded to a certain extent, a superimposed pulsating component of illumination is introduced, causing the illuminated LED to begin to flicker, informing the user that the battery voltage is nearing insufficient values. As battery voltage drops further, the steady component of illumination ceases altogether, and the flicker converts to on-off blinking, indicating that the battery voltage is at the verge of an insufficient value. When the battery voltage drops fruther, the LED ceases to be illuminated. During part or all of the flicker phase, and/or during part or all of the blinking phase, the frequency of the pulsating component of illumination progressively increases with decreasing battery voltage, to create an effect of increasing urgency.