Abstract: A phototransistor is provided with a first resistor that operates as a shunt and a second resistor that operates to protect the device from damage that could be caused by a reverse bias condition. The possible damage results from the creation of a PN junction relationship caused by the doping of N conductivity type material with P.sup.+ conductivity type material in order to form the first resistor. This junction relationship creates a parasitic diode that provides a current path between the emitter and collector terminals of the phototransistor. In order to prevent damage that might occur during a reverse voltage connection, a second resistor is connected between the emitter of transistor Q.sub.1 and the first resistor. The second resistor is in series with the junction relationship resulting from the structure used to form the first resistor and therefore serves to limit the current flowing between the emitter and collector terminals of the transistor under reversed bias conditions.

Abstract: An arrangement for terminating a tap-off line (40) between a bus line (14) and a bi-directional signal driver (38). The arrangement includes a resistor (42) serially connected in the tap-off line and a controllable switch (44) connected across the resistor. There is also provided means (46, 48) for controlling the switch to bypass the resistor when the bi-directional signal driver transmits signals to the bus.

Abstract: A circuit for connecting the power supply output of a computer to ground when the system is shut down to counter adverse effects of backfeed voltage which includes a MOSFET between the power supply output and ground. In one embodiment the MOSFET is switched on by a signal that deactivates the system power supply. In an alternative embodiment, two MOSFETs are used. The first MOSFET is controlled directly by the power supply output and shorts the second MOSFET's gate to ground when the power supply output generates a significant voltage. If the second MOSFET's gate is grounded, the MOSFET deactivates and opens a circuit between the power supply output and ground. When the power supply is turned off, the second MOSFET activates and grounds the power supply output. A resistor between the power supply output and ground allows the power supply to generate five volts when the system is power cycled and deactivate the second MOSFET.

Abstract: An arrangement for protecting an integrated circuit device (11) against latch up during a nuclear event comprising a capacitance (15) and a switch (17) connected in parallel across the power supply lines (13) of the device. When the power supply lines are connected to a power supply (19) the capacitance stores energy sufficient to supply necessary operating currents to the device during its normal operation. The switch is arranged so that, under a transient gamma pulse incident thereon during a nuclear event, its impedance is set to a low value at such a rate that the energy stored by the capacitance is discharged through the switch and the voltage applied to the device via the power supply lines is pulled down to such a level and at such a rate as to prevent transient gamma pulse induced latch-up in the device.

Abstract: A feeding system is provided for supplying a current to repeaters on a communication cable including a feed line for conducting a current to the repeaters. The feeding system includes a plurality of branching units provided on the communication cable and terminal stations each being connected through at least one of the repeaters to one of the branching units, and each of the terminal stations feeding a current through the feed line to the repeaters. In addition each of the plurality of branching units includes at least one switching circuit for switching to connect the at least one of the repeaters to the communication cable or to the ground, depending on the amount of current conducting through the feed line in the communication cable. Further, the current thresholds of the switching circuits in the plurality of branching units are preferably different from each other.

Abstract: A battery in a back-up power system is charged during the time that power is available from the main AC power system by utilizing the main power transformer and the main inverter. When power is available from the main AC power source, an AC voltage appears across the primary of the transformer, which is connected to the inverter. Switches in the bridge inverter are turned on for a relatively brief period of time to short the primary of the transformer causing current through the leakage inductances of the transformer to rapidly build up. When the switching devices are turned off, the inductances induce a current to continue to flow from the primary into the inverter through anti-parallel diodes, normally back biased by the voltage from the battery, into the battery thereby charging the battery with the energy stored in the transformer inductances. The inverter current reaches zero when the energy stored in the inductance is fully discharged.

Abstract: An electrostatic discharge protective apparatus for an integrated circuit having normally on semiconductor devices mutually connecting input/output pads and the power in bonding pad to prevent stray electrostatic discharges from damaging the integrated circuit components when the integrated circuit is not powered on. All adjacent input/output pads are connected to each other by a normally on transistor. Each pad is additionally connected to a power supply pad by a normally on transistor.

Abstract: The improvements consist in constructing the bridge cap on the basis of an electrically insulating frame (8) and a dissipating plate (1), such plate comprising an external and larger metal-based layer (4), a thin middle electrically insulating and good heat conducting layer (5) and an internal layer (6), preferably made of copper, on which the tracks (6') are defined to attach, by tin welding, rectifier cells (2) and their relevant connectors (7) and connecting tags (3) to the outside.

Abstract: A device for protecting electronic equipment (42) against strong electromagnetic pulses, the equipment being contained in a radioelectrically insulated enclosure (40) and connected to a line outside the enclosure, the protective device being disposed in another radioelectrically insulated enclosure (2) and comprising an input (4) connected to said line (6) and an output (8) connected to the equipment, the device being characterized in that it comprises in series: at least one first clipping cell (12A) comprising a clipper having one end connected to the input of the clipping cell and another end to ground, and a low-pass filter disposed between the input and the output of the clipping cell, and a filtering cell (14) comprising in series a low-pass filter (12A) and if necessary a device (14B) for switching the cut-off frequency of the filter. The device is particularly applicable to the protection of telephonic and digital lines.

Abstract: A semiconductor device having an input protection circuit is disclosed. The semiconductor device includes a power-on reset circuit which generates a pulse having a pulse width determined according to an input surge, applied to an input terminal when an input voltage has risen to a preset level. In response to a pulse generated by the power-on reset circuit, a CMOS inverter supplies a predetermined voltage to the base of a bipolar transistor and controls the bipolar transistor so that it clamps an input voltage supplied thereto to a voltage level lower than the withstanding voltage of the internal circuit in a period corresponding to the pulse width. Thus, the input protection circuit constituted by the bipolar transistor clamps an input voltage, supplied by the input terminal to the internal circuit, to a predetermined level.

Abstract: A method for minimizing false alarms and background electronic noise in an electronic article surveillance system operated in the vicinity of substantially closed electrical loops such as formed by metal door and window frames. If the conductance of such loops is variable, electric currents induced in such loops by electromagnetic fields produced by the system have been found to be discontinuous, and can both produce a false alarm and raise the background noise level. The method comprises connecting metal straps across all joints in such loops to ensure permanent, reliable electrical connections at all such joints, thus providing greatly reduced variations in conductance around the loop.

Abstract: This invention is concerned with a circuit arrangement for reducing the residual voltage on partially disconnected loads, such as control coils of electromagnetic switchgear having long control lines, by connecting an auxiliary load in parallel to the load. According to the invention, a constant-current sink is connected in parallel to the load as an additional load, which is dependent on a control circuit that the circuit closes when the applied voltage is below a predetermined value and breaks when it exceeds a predetermined value.

Abstract: Security equipment comprises a plurality of normally-open or normally-closed switch contacts connected in a loop circuit to a central control circuit. Each pair of switch contacts has a respective resistor connected in parallel therewith and the control circuit is operable to detect changes in resistance due, for example, to an intruder operating one of the switches.

Abstract: A current supply circuit for electronic equipment of an automotive vehicle having an additional relay being energized by the ignition switch at its starter position. In this starter position, the relay is operated and the battery current is directly supplied to the electronic equipment at the time of starting the vehicle to avoid abrupt decrease of the source voltage.

Abstract: An electrosurge generator, which is energized by a power supply to produce n output voltage of a desired level, includes a failsafe system at its output to prevent any excessive high DC voltage output which may result from a failure in the electrosurge generator. The failsafe system has a detection element coupled to the output of the electrosurge generator which detects any output above a predetermined threshold. A switching circuit is activated by the detection element. The switching circuit is connected across the power supply, and when activated, removes the power supplied from the power supply to the electrosurge generator.

Abstract: Digital interface circuitry is utilized to analyze the condition of alarm detecting loops. The new circuitry is utilized as an alarm system of the type which has a detecting loop extending between a central station and a remote zone at which is provided a normally open detection switch in parallel with a resistor. At the central station a digital high voltage is supplied to the input loop lead and a resistor is connected to ground from a reference point on the return lead, to provide a voltage divider network with the remote resistor. Two voltage-sampling branches connect to the reference point; the first branch has a comparator or pull-up circuit to indicate digitally whether the voltage level is substantially zero or greater, while the second branch has a level detector and pull-up circuit or a comparator to indicate digitally whether the reference point voltae is greater than its normal level.

Abstract: The intermediate current transformer is replaced by a shunt resistor which bridges the secondary winding of the main current transformer and is of such magnitude that the secondary winding of the main current transformer is virtually short-circuited, but the voltage at the shunt resistor is still sufficient for evaluation in the electronic relay. The shunt resistor consumes only very little power and can therefore be located in the base of a plug-in device. This base, being a permanent part of the assembly, remains in circuit even when the relay is changed or removed for inspection or testing purposes.

Abstract: A solid state transmit-receive switching element having multiple resonant rcuits connected in a bridge arrangement by back-to-back zener diodes. While receiving, the zener diodes have a high impedance and the bridge arrangement acts as two series tuned circuits in parallel. While transmitting, the zener diodes breakdown and the bridge arrangement appears electrically as two parallel tuned circuits in series.

Abstract: Each of a plurality of switches is connected in parallel with an impedance and the switches are coupled to form a series circuit. A reference voltage is coupled to one end of the series circuit and a termination impedance is coupled to the other end to form a voltage divider. The voltage divider ratio is determined by the switches that are operated and the divided voltage is coupled to an analog-to-digital converter producing a binary output signal that indicates which combination of switches is operated. Another embodiment of the invention uses a constant current generator instead of a termination impedance to provide linear ratios in the voltage divider.

Abstract: A stereo indicating circuit for use with an FM receiver having a multiplex demodulator, a stereo indicator and a stereo-monaural mode selector, the stereo indicating circuit comprising a smoothing circuit having a short time constant for changing the mode of the FM receiver from stereo to monaural and immediately turning off the stereo indicator after the power switch of the FM receiver is turned off by utilizing the sharp voltage drop of said smoothing circuit.

Abstract: To eliminate the recording of undesirable sounds which can occur upon stang a sound motion picture camera in which sound is recorded simultaneously as the picture is recorded, a circuit shorting switch is installed in parallel with the sound recording head, and a film transport motor control switch is arranged to function opposite to the circuit shorting switch but in cooperation with that switch to stabilize the amplifier before film movement begins.

Abstract: No-load losses normally associated with transformer-isolated inverter circuits employing high frequency switching devices are substantially eliminated by electrically short-circuiting the load terminals of the inverter to quickly and efficiently shut down inverter operation and thereby reduce the no-load losses to at least the fall-back current losses of the inverter.