Abstract: A protection circuit against an excessive current in a flyback transformer which supplies a high voltage to a CRT. A fuse and current detecting resistor are inserted on the line which supplies a current to the primary winding of the flyback transformer. The intermediate point of the primary winding and the node of the fuse and current detecting resistor are connected by a semiconductor switching element which becomes conductive when the voltage across the current detecting resistor reaches a certain high voltage. Accordingly, if an excessive current flows in the flyback transformer, the thyristor turns on, causing the fuse to be blown by the large current, whereby the current supply to the flyback transformer can be shut off.

Abstract: A power transistor having a control electrode which is coupled to a polysilicon JFET transistor is provided. In particular, a power MOSFET device having a polysilicon gate is formed and a JFET transistor is formed in the same polysilicon layer which forms the gate of the power MOSFET. A drain of the JFET forms an input terminal for the power MOSFET and a source of the JFET is coupled to the gate of the power MOSFET. A gate of the JFET is coupled to a gate-drain diode clamp so that when the gate-drain diode clamp is activated a portion of the current which is used to turn on the power MOSFET is channeled to the gate of the JFET and increases the drain-to-source series resistance of the JFET. The resistance of the JFET is low during normal operation and increases only when the gate-drain clamp is activated thus provides a high resistance during avalanche stress protection and a low resistance during normal operation.

Abstract: In addition to a circuit for clamping a power supply voltage supplied from a power supply to a rated voltage, a circuit for clamping the power supply voltage to a voltage of less than the rated voltage is arranged. Even if it is necessary to flow a large current into the voltage clamping transistor for overvoltage protection, a large current can be flowed within a safe operating area of the transistor if the transistor is operated at a low voltage. Damage of the voltage clamping transistor or degradation of reliability can be prevented.

Abstract: The invention relates to a protective circuit for the induction coil of a magnetically inductive type flow meter. If the leads of a flow meter used in an explosive environment are cut there can occur a high voltage and resulting sparking which could cause an explosion. The invention provides a circuit in which a short circuit path is provided for the induction coil if the leads thereof are severed to prevent the development of a high voltage which could cause dangerous sparking.

Abstract: A protection arrangement for a two-wire line, such as a telephone subscriber line, includes a transformer having two primary windings and a secondary winding. The primary windings are connected in series with the wires of the line with phases such that common mode (longitudinal) currents on the line induce a current in the secondary winding, whereas loop currents do not. The induced current in the secondary winding is amplified and used to trigger a protection device, such as a triac or SCR and diode bridge arrangement, to short circuit the line for the duration of any excessive current thereon.

Abstract: An apparatus for protecting the fault current intolerant elements of a motor starter circuit or the like is comprised of a protective shunt which bypasses the fault current intolerant elements in response to the detection of high fault currents. The protective shunt is formed of a "U" shaped conductor which flexes in response to the magnetic field created by the flow of the high fault currents through the "U" shaped conductor. Electrical contacts place on one leg of the "U" shaped conductor and on a stationary conductor form a shunting switch which conducts high fault currents around the starter circuitry. In a second embodiment, the stationary conductor is replaced with a flexible conductor which carries an armature. The magnetic armature is attracted by a focussed magnetic field from a magnetic yoke positioned around one leg of the "U" shaped conductor.

Abstract: A solid state circuit protector is comprised of a coil winding, a latching type Hall effect device, and a solid state switching network including an NPN bipolar junction transistor with a current limiting resistor. Other types of solid state switches can be employed instead of or in addition to the bipolar junction transistor.

Abstract: A lamp output protective circuit for an electronic controller having a first npn transistor connected to an output terminal through which a lamp is supplied with electric power, a resistor connected between the emitter of said first npn transistor and the ground, and a second npn transistor having its collector connected to the base of the first npn transistor, its emitter to the ground and its base to a point between the emitter of the first npn transistor and the resistor. The base of the first npn transistor and the collector of the second npn transistor are connected to a signal line of the electronic controller connected to a power source.

Abstract: A short-circuit protected switched output circuit having: an input node (I10) for receiving an input switching signal; an output node (O10) for outputting a switched output signal; switch means (Q10) connected between the input and output nodes; and a Schmitt trigger NAND gate oscillator arrangement (C10, D11, D12, NG10, R12, R13, R14) having an input coupled to the output node and having an output coupled via diode means to the input node, whereby the oscillator arrangement produces a low frequency, low duty-cycle, fixed-frequency signal at the output node in the event of the output node being short-circuited. An alternative circuit using a Schmitt trigger inverter are also disclosed.

Abstract: An automobile alternator regulator integrated circuit having a voltage-supply or -sense node (6) for connection to an external voltage, and a voltage clamp comprising: a pnp bypass transistor (Q1) having a base electrode, an emitter electrode coupled to the node and a collector electrode coupled to ground; a resistor (R1) connected between the base electrode and the node; a Zener diode (Z1-Z4) connected between the base electrode and ground for enabling the bypass transistor when the voltage at the node exceeds a predetermined value, whereby the voltage at the node is clamped to a voltage no greater than the predetermined value; and a fuse (F1) connected between the node and the emitter electrode so as to provide a subsequently identifiable cause of failure if the fuse becomes blown due to excess voltage while allowing subsequent operation of the integrated circuit if the clamp means fails but another part of the integrated circuit remains functional.

Abstract: A single-channel shunt-diode safety barrier for energizing a 2-wire transmitter, particularly for use in process control, incorporates within the barrier a floating d.c. power supply or its equivalent to enable the barrier to deliver into an earthed load a direct current substantially equal to that which it draws from the transmitter. The floating d.c. power supply is preferably derived from an external d.c. power source via a transformer or diode-pump circuit within the barrier itself. The barrier is enabled to pass superimposed digital or frequency signals in both directions to and from the transmitter.

Abstract: A ballast assembly has a thermal circuit protector with a resistor mounted in close proximity, for protecting multiple coils in a ballast assembly. The thermal circuit protector is included in the assembly, connected in series with a first coil. The resistor is connected in series with a second coil, with the resistor sized to produce sufficient heat during a high current draw condition to actuate a bimetallic switch within the adjacent protector, thereby interrupting power to the ballast assembly and preventing damage without requiring a second thermal circuit protector.

Abstract: Series capacitor equipment for distribution networks has a capacitor, voltage-dependent resistors as over-voltage protective means for the capacitor, a mechanical high-speed circuit-closer and a switch connected in parallel with the high-speed circuit-closer, for bypassing the equipment. At an overcurrent in the power line, tripping members initiate closing of the high-speed circuit-closer, which closes rapidly sufficient to protect the resistors against overload, and of the switch, which relieves the high-speed circuit-closer. The high-speed circuit-closer, the switch and the tripping members are mounted in a grounded cubicle.

Abstract: A two-wire telephone subscriber line protection arrangement consists of two protection devices each comprising a pair of complementary thyristors connected in reverse parallel with one another between a respective wire and a reference point, with their gates connected together and directly to a control terminal which has a connection to the wire via a resistance which determines an overcurrent threshold level for the device. The reference point is ground for the ring wire protection device, and is desirably the ring wire for the tip wire protection device, whereby a directional sensitivity of the protection devices is taken advantage of and the overcurrent threshold level can be reduced. Zener diodes connected between complementary thyristors provide for convenient overvoltage protection.

Abstract: A protective circuit for a semiconductor laser supplied with an excitation current by a current generator circuit is created using a transducer, whose output is controlled by the laser light, a limit circuit cooperating with the transducer and a current shunt circuit energized by the limit circuit and switched in parallel with the semiconductor laser. Once the permissible emitted light power is reached, excessive excitation current is diverted to the shunt circuit. Exemplary embodiments of the invention are found to achieve response times below 20 ns and are able to protect the semiconductor laser from overload currents even during power-on and power off.

Abstract: Protective circuits for preventing fires due to arc short circuits (as opposed to dead short circuits), are described. Current flow in excess of that existing during normal transient overloads is indicative of an arc short circuit. Protection is provided by triacs which are triggered by circuit current flow in excess of that existing during normal transient overloads. When triggered, the triacs, in series with the fuse or circuit breaker, are placed directly across the power source and thus actuated substantially instantaneously to interrupt current flow to the load circuit. By thus interrupting current flow the hazard of a fire is obviated. Means are also provided for giving a visual indicium that the protective circuit has been actuated by triggering of the triacs. Additional means are provided for triggering the triacs in response to an overheated main electrical service connection.

Abstract: A circuit for protecting sensitive telephone equipment from voltage or current overloads on the TIP or RING line includes a resistor serially positioned in the line and a triac triggered by a voltage differential across the resistor. A pair of fast diodes is positioned on the line adjacent to the telephone equipment for momentarily clamping the voltage on the line at that point between ground and the voltage supply of the equipment. The mementary clamping of the voltage creates the voltage differential across the resistor which triggers the triac. The fast diodes are capable of passing current for a time sufficient to allow the triac to begin shunting current to ground. An enhanced form of the protection circuit includes a second pair of diodes extending in parallel with the fast pair of diodes and positioned on the line between the pair of fast diodes and the triac. Inclusion of the second pair of diodes allows the circuit to utilize a triac with a slower turn-on time and a higher on-state voltage.

Abstract: A transistor protective circuit includes a transistor transmitting a current to a load to drive same, and a switching element provided in a preceding stage of the transistor and responsive to an abnormal current in the load to turn off the transistor to protect it against destruction.

Abstract: A semiconductor module includes two switching devices operated by the PWM control signal, current detectors for detecting currents through the respective switching devices, and bypass units operated by the corresponding opposite current detector for shunting the control signal to the respective switching devices to prevent activation thereof when the corresponding opposite switching device is conductive.

Abstract: A D.C. motor control circuit for a dentist's hand drill including a feedback loop to vary the torque of the motor according to the load on the motor while keeping the motor speed constant. Power to the motor is provided through a three terminal regulating IC circuit. The IC regulating circuit is protected against power surges by an overload detecting circuit incorporated into the feedback loop.

Abstract: Circuit protection devices which comprise a PTC conductive polymer element and a second electrical component which is thermally coupled to the PTC element and which, when a fault causes the current in the circuit to become excessive, generates heat which is transferred to the PTC element, thus reducing the time taken to "trip" the PTC element. The second component is for example a voltage-dependent resistor which is connected in series with the PTC element under the fault conditions and is thus protected from damage.

Abstract: A permanent magnet generator and rectifier is connected to the exciter of an alternator and a separate rectifier provides a D.C. voltage supply to a voltage regulator. A thyristor is connected in series with a second fuse across the exciter rectifier to short circuit the supply in series with a main external fuse. If the main fuse fails to open, the second fuse opens. The second fuse is potted in the regulators to prevent tampering. An overexcitation and a low voltage demand signal are sensed. The two signals are coupled to a NAND logic gate to produce an output shut-down signal. If either even is established and the first produces a signal, a shut-down signal is generated to a second comparator amplifier of latch circuit. A delay circuit connects the shut-down signal to a triggered oscillator for firing the thyristor.

Abstract: Load current is diverted from a circuit breaker, when it is opened, through a commutation circuit. The latter has a capacitor, inductance and solid state switch serially connected with the output of a bridge rectifier. The input of the bridge is connected across the breaker. The switch is turned on to discharge the precharged capacitor to form a current pulse, presenting an extremely low resistance across the bridge input and causing load current diversion.

Abstract: A two-terminal A.C. device is described which can be series connected with a lighting fixture to prevent overheating of the fixture in an overload condition, namely, when a lighting element exceeding the power rating of the fixture is installed. In broad terms, the device includes a bidirectional, self-extinguishing switch which can be triggered to conduct current between the two terminals of the device, and control circuitry operable from the voltage difference and current between the two terminals occurring in use to regulate the triggering of the switch. The control circuitry includes triggering circuitry which generates triggering signals from the voltage difference across the terminals of the device and normally applies the triggering signals to the control terminal to permit a predetermined measure of conduction.

Abstract: A crowbar circuit is provided in an inverter for diverting overcurrents from the inverter switches. The crowbar circuit includes a crowbar switch and a crowbar winding which is magnetically coupled with the inverter snubber reactors. The size and the coupling of the crowbar winding are chosen so as to reduce or make negative the di/dt of the snubber reactors when the crowbar switch is turned on.

Abstract: A digital power converter input current control circuit is connected between a power converter and a power source. This circuit monitors, and controls if necessary, the current that flows between the power source and the power converter in a manner that protects the power source, the input current control circuit, and the power converter from the catastrophic effects of excessive current flow. The input current control circuit operates similar to an electronic circuit breaker with an automatic reset feature, in that the power delivered to the power converter is maintained low during fault conditions. Thus, if a power transistor in the power converter should fail, a current limit circuit in the input current control circuit will prevent additional damage to the power converter.

Abstract: A fault sensing system for protecting a transformer, the system including a partial range current limiting fuse connected in series in the primary circuit for the network transformer, a normally open vacuum switch connected to the primary circuit and shunted to ground between the current limiting fuse and the transformer, a solenoid actuated assembly for closing the vacuum switch and a fault sensing circuit assembly operatively connected to energize the solenoid assembly, the fault sensing circuit being normally de-energized and including a current transformer mounted on the primary circuit and a low voltage fuse element connected across the current transformer, the fault sensing circuit assembly being energized on operation of the low voltage fuse element to momentarily energize the solenoid.

Abstract: In order to protect converter equipment which includes GTO switching-off thyristors and having d-c inputs and a protective inductance connected in series therewith against short circuit currents, a short circuit path for d-c current flowing from a d-c supply source on the one hand, and on the other hand, an energy storage device, is inserted into the d-c circuit, closed via an auxiliary thyristor, of the converter equipment in such a manner that through the change of the state of storage of the energy storage device, a countervoltage is impressed on the d-c terminals, which leads to the forcible commutation of the switching-off thyristors. The energy storage device advantageously comprises an auxiliary winding of a limiting choke serving as a protective inductance.

Abstract: An inrush current limited power supply includes a regulator with a capacitor coupled across its input terminals. If voltage to be regulated is suddenly applied by a switch to the input terminals of the regulator, an undesirably large current surge occurs as the capacitor charges. The magnitude of the current surge is limited by a surge limiting resistor coupled in series with the switch. This limits the surge current, but undesirably causes power dissipation in the resistor during normal operation. The channel of a FET is connected across the resistor. The FET has a conductivity which is low when the gate-to-source voltage is low, for preventing large inrush current immediately after turn-on. A control voltage generator generates a control voltage by rectifying an alternating voltage, and it is coupled to the gate and source of the FET. In one embodiment, the control voltage generator is referenced to an input terminal of the regulator. In another embodiment it is referenced to output terminal.

Abstract: Input/output circuitry is disclosed for use in an I/O system of a programmable controller. The circuitry is protected against overcurrents without the use of fuses or circuit breakers, and is automatically restored to normal operation following correction of an overload condition. Diagnostic signals are produced for monitoring the operating condition of the circuitry. The invention includes an insulated gate transistor (IGT) having a main current section carrying a majority of the load current and an emulation section which carries a fractional portion of the load current. The emulation section current tracks the total current at all times. A current sensor monitors the emulation section current and provides a signal representing the instantaneous load current. This signal is continuously compared with preselected reference levels to derive a set of diagnostic signals that are indicative of the operating condition of the circuit, and whether output loads are open or shorted, for example.

Abstract: A hybrid solid state/mechanical switch is provided with a pair of mechanical contacts connected in parallel with a solid state switching device. These components are operated by a control circuit to achieve arcless current interruption under normal conditions. A circuit breaking device, which can be operated by a crowbar circuit, provides failure protection for the hybrid switch if excessive leakage current is detected in the solid state switching device or current continues to flow through the switch at a preselected time following the occurrence of a turn-off command signal.

Abstract: An integrated circuit protection device for use with a voltage regulator used to drive an integrated circuit to prevent damage to the integrated circuit which goes into a "latch up" condition. The integrated circuit protection device comprises a first switching circuit, connected to the output of the voltage regulator for selectively connecting the output of the voltage regulator to ground and a second switching circuit, connected to the input and the output of the voltage regulator and to the first switching circuit, for detecting a "latch up" condition and for selectively activating the first switching circuit upon detection of a "latch up" condition, whereby the first switching circuit connects the output of the voltage regulator to ground and resets the integrated circuit to prevent damage thereto. A predetermined time after the "latch up" condition is detected, normal operation is automatically restored.

Abstract: A proximity effect heat-tracing system in which proximity effect heat-tracing circuits are fed in either direction from a plurality of feed points connected to a single main transformer to increase the length of pipeline supplied by a single main transformer. A secondary transformer interposed between a main transformer and a plurality of feed points reduces the voltage required to be applied to a proximity effect heat-tracing system of a given length. Two or more proximity effect heat-tracing systems used along the same length of pipeline, employ neutral conductors having approximately the same diameter as "hot" conductors where the secondary of the main transformer in each system is 180.degree. electrically out of phase with the secondary of the main transformer in the other system.

Abstract: Methods and apparatus for detecting abnormalities in proximity effect pipeline tracing circuits by coupling conductive elements carrying proximity effect circuit currents and having opposite polarities. These conductive elements are coupled to an additional conductive element which is in turn connected to a system for detecting current so that when the difference between the proximity effect circuit currents is non-zero, the current flows through the additional conductive element and is detected by a relay or ammeter.

Abstract: A semiconductor fuse is disclosed that provides protection against both overcurrent and the abrupt application of a voltage to semiconductor devices. A first means is coupled to an input terminal for providing a signal when a current is applied to the input terminal. A second means is coupled between the input terminal and an output terminal for allowing current to pass therebetween and is coupled to the detecting means and responsive to the signal. A third means is coupled between the output terminal and a ground terminal for shorting a current therebetween. A fourth means is coupled to the input terminal, the second means, and the third means for activating the third means and preventing the second means from responding to the signal when the input current exceeds a predetermined value.

Abstract: A protective means for a series capacitor in a high-voltage network comprises a voltage-dependent resistor (varistor) arranged in parallel with the series capacitor, a spark gap arranged in parallel with the varistor for shunting the latter when it becomes overloaded, a current-sensing member, for example a current transformer, for sensing the current through the varistor, an energy absorption detector for sensing the temperature of the varistor, and a pulse transformer electrically or magnetically connected to the current-sensing member, for triggering the spark gap. During normal operation of the network and the series capacitor the current-sensing member is short-circuited by a normally closed switching device.

Abstract: The rectifiers for generating direct-currents or hybrid or complex currents for inductive loads must be protected against fault currents which can arise due to faulty operating conditions in the load inductance, by providing for a rapid current cutoff. The heretofore known electronic protective circuits are not suitable for this purpose because the excitation circuit connected in parallel with the load only contains one diode which, in the case of complex currents with large control angle and the thus caused negative voltage peaks, conducts the current during the duration of such voltage peaks, so that the deexcitation circuit periodically only acts as a shunt circuit for the load. To avoid this drawback the new and improved protective circuit contains a controlled valve in the deenergization or deexcitation circuit.

Abstract: A protection circuit for communication equipment connected to a two conductor communication line includes a bridge rectifier having alternating current terminals connected to the conductors and to ground. The direct current terminals of the rectifier are connected to a device responsive to a range of predetermined voltage and current conditions in the conductors for reflecting foreign electrical energy.

Abstract: Safety apparatus for a motor vehicle electric consumer having a temperature-dependent internal resistance, which includes a temperature indicating circuit for providing a signal which accurately indicates the consumer temperature to a threshold switch which actuates a switching device to interrupt current flow through the consumer whenever the consumer temperature exceeds a predetermined maximum value. The temperature indicating circuit either may be a consumer resistance measuring circuit such as a bridge circuit including the consumer in one leg thereof, or may be a consumer temperature replicating circuit, connected in parallel with the consumer, such as a special RC network. The switching device either may be a switch connected in series with the consumer, or a switch connected in parallel with the consumer, in which case the apparatus also includes an overcurrent device connected in series with the parallel combination of the switch and the consumer.

Abstract: An apparatus and method of drying a transformer by applying current to a winding thereof in a controlled fashion. Alternating with periods of applying the current to the winding, the electrical resistance of the winding is periodically measured using a bridge circuit. The application of the current is controlled, dependent on the results of the resistance measurements, to discontinue the application of current when the measured resistance is equal to or greater than a preset resistance. The current application is resumed when the measured resistance falls below the preset resistance. In a preferred form insulation resistance is tested by measuring leakage current after each measurement of winding resistance and when leakage resistance reaches an acceptable level the apparatus is shut down.

Abstract: An overcurrent protection system adaptable for use with power controllers the single or multi-phase ac, or dc types includes a load current sensing element in combination with an overcurrent sensing/inverse time delay circuit, a power switch and a crowbar circuit. The system also includes a drive circuit, a drive circuit input current sensor, a trip signal detector and a logic circuit. The overcurrent protection system, according to the present invention, uses the drive circuit to power the overcurrent sensing/inverse time delay circuit, to drive the power switch, and to provide a coupling path for an overcurrent fault signal across electrical isolation interface(s) thereof to the logic circuit. Thus, the need for a separate isolated power supply for powering the overcurrent sensing/inverse time delay circuit and the need for separate optical and/or electromagnetic isolation interfaces for coupling of the overcurrent fault signal are eliminated.

Abstract: A fault detector for detecting shoot-through conditions in series connected solid state rectifiers (326, 329) of a power inverter (314) is disclosed. A capacitor (311) discharges when a shoot-through occurs and the discharge current is detected by a current transformer (315). An SCR (317) is gated on by the detector to short circuit the DC bus (327, 328) and prevent damage to the solid state rectifiers (326, 329).

Abstract: A d.c. motor whose armature is supplied from an a.c. power source through an a.c./d.c. thyristor converter and is subject to damaging commutator flash-over, as from loss of a.c. voltage during regeneration is provided with a protective circuit which includes a normally charged capacitor and a diverter resistor which are connectable across the converter and motor armature, respectively, by SCR means in response to a fault condition such as either predetermined high output current from the converter (i.e., indicative of high armature current) or excess a.c. input current to the converter. Connection of the capacitor across the converter and its discharge instantaneously and forcibly but temporarily blocks current flow from the converter thyristors to the motor armature.

Abstract: The invention provides an improved circuit for determining rates of rise of energy in metal oxide varistor devices. A high voltage transformer is employed to trigger a protective air gap for bypassing the metal oxide varistor device. One application for the invention is for use within a series capacitor protective circuit.

Abstract: A surge voltage arrester utilizes for surge protection a varistor of the zinc oxide type between a line terminal and a ground terminal. The varistor is of a type that has a resistance which decreases as increasing voltage is applied thereacross. With increasing temperature the leakage current through the varistor increases at a given voltage. At a critical temperature and voltage condition, the varistor is subject to a thermal runaway condition which would cause the varistor to fail expelling hot particles. To avoid this failure condition, a fail-safe mechanism is provided which connects the line terminal to the ground terminal by-passing the varistor when there is an overcurrent condition on the line that results in heating of the varistor.

Abstract: This current limiting device comprises a normally-closed source-side circuit interrupter, a normally-closed load-side circuit interrupter, an electrical conductor connected between the interrupters for connecting the interrupters in series, and a normally-open switch that can be closed to connect the conductor to ground via a low-impedance conductive path located electrically between the interrupters. A switch operator acts to rapidly close the switch in response to a fault on the power circuit extending through the series combination of interrupters, thereby connecting the conductor to ground through the switch. The switch operator closes the switch within 1/4 cycle of power frequency current after fault inception, thereby effecting current-limiting action with respect to current through the series combination of interrupters on the load side of the conductive path to ground.

Abstract: The invention provides a circuit for determining excessive energy magnitudes or rates of rise of energy in metal oxide varistor devices. The circuit further provides a series of low voltage control pulses for energizing a high voltage pulse generator. The output of the high voltage pulse generator triggers a protective air gap for bypassing the metal oxide varistor device. One application for the invention is for use within a series capacitor protective circuit.

Abstract: A safeguarded integrated circuit includes two supply electrodes, an output electrode and an input electrode. Between two of the electrodes there is provided a protection circuit having a lateral bipolar transistor, the emitter and collector zones of which are connected respectively to the said electrodes. The bipolar transistor is provided in a region which is surrounded by the substrate which region serves as a base zone and has a conductivity type opposite to that of the substrate. A connection contact connected to the emitter is provided on this region and a modulatable resistance is formed between the connection contact and the active base zone by the region.

Abstract: A high speed fault diverter switch is connected near the input side of a gas-insulated substation. The switch is normally open and is used in response to arcing anywhere within the substation to connect the gas-insulated high-voltage conductor to ground for each phase of the system at high speed to divert the fault current to ground.

Abstract: A signal distribution circuit subject to high-level reverse-current transients is protected by the combination of a reverse-current sensor and a controlled current shunt. The sensor detects a potentially damaging reverse-current current surge and sends a control signal to the current shunt. The current shunt then diverts the surge away from the distribution amplifier which consequently can have a low power rating. After the transient subsides, the circuit is automatically reset to allow continuation of normal signal distribution.