Abstract: A telephone line protection element constructed of three lead frames having contact fingers for holding therebetween a semiconductor cell providing overvoltage protection between the telephone line and the customer circuits. The lead frames are soldered to a resistive semiconductor material to provide a fail-safe mechanism that mechanically connects either the tip or ring telephone line conductors to ground if a sufficient overcurrent exists. In response to an overcurrent, the resistive semiconductor material generates heat and melts the solder in contact therewith, which allows a pre-bent member of the lead frame to move in contact with a ground terminal, thereby shunting the overcurrent to ground. The entire protection element includes very few components and is efficiently assembled and attached to the pins of a 5-pin module.

Abstract: An overvoltage protection device having multiple shorting dots in the emitter region and multiple buried regions substantially aligned with these shorting dots. The placement, number, and area of these buried regions reduce and more accurately set the overshoot voltage value of the device while maintaining the high surge capacities of the device. Further, doping types and concentrations have been modified from that known in the prior art to reduce overshoot providing a more accurate and sensitive overvoltage protection device than that known previously in the prior art.

Abstract: A two-terminal, bidirectional semiconductor trigger switch is provided. The trigger switch is a relatively sensitive multilayer semiconductor breakover device that switches on fully when its breakover voltage is reached. The design of the trigger switch allows its breakover voltage point to be readily adjustable during fabrication of the device.The semiconductor trigger switch is particularly suited to provide a low voltage trigger for a TRIAC. The trigger switch is connected in series with the gate of the TRIAC and mounted on the gate lead to provide a unitary, three-terminal device incorporating the TRIAC/trigger switch combination.

Abstract: An overvoltage protection circuit for electronic equipment having tip and ring lines includes a first voltage sensitive switch having first and second teminals. The first terminal of the first switch is connected to the tip line. A second voltage sensitive switch includes first and second terminals. The first terminal of the second switch is connected to the second terminal of the first switch, and the second terminal thereof is connected to the ring line. A third voltage sensitive switch includes first and second terminals. The first terminal of the third switch is connected to the second terminal of the first switch and to the first terminal of the second switch. The second terminal of the third switch is connected to ground potential. The switches are conductive when a respective voltage threshold is exceeded.

Abstract: A telephone maintenance termination unit utilizes a low voltage, bidirectional trigger switch for performing diagnostic functions on a telephone line. The trigger switch provides low voltage, low current triggering in conjunction with a high holding current requirement. The trigger switch may comprise either two silicon controlled rectifiers connected in inverse parallel relationship with their gates connected, a bidirectional diffused PNPN semiconductor device, or an NPN semiconductor device, any one of which is used to trigger a power control TRIAC. In another embodiment, the switching device may be a two-terminal, unitary semiconductor device incorporating the functions of both the TRIAC and the bidirectional trigger switch.

Abstract: A telephone maintenance termination unit utilizes a low voltage, bidirectional trigger switch. The trigger switch provides low voltage, low current triggering in conjunction with a high holding current requirement. The trigger switch may comprise either two silicon controlled rectifiers connected in inverse parallel relationship with their gates connected, a bidirectional diffused PNPN semiconductor device, or an NPN semiconductor device, any one of which is used to trigger a power control TRIAC. In another embodiment, the switching device may be a two-terminal, unitary semiconductor device incorporating the functions of both the TRIAC and the bidirectional trigger switch.

Abstract: A method of controlling the speed of an alternating current motor is disclosed. A direct current reference signal, the magnitude of which is proportional to the speed of an electric motor, is coupled to one input of a voltage comparator. A control pulse is generated at the beginning of each half cycle of the alternating current source and utilized to periodically discharge a timing capacitor. The voltage present on the timing capacitor is applied to a second input of the voltage comparator and when the timing capacitor voltage equals or exceeds the direct current reference signal, power is applied to the motor.

Abstract: A control circuit is disclosed for limiting the polarity and duration of current flowing through an electromagnetic device which is coupled to an alternating current potential source. The control circuit is coupled in series with the electromagnetic device and a switch. The control circuit includes a gate controlled conduction device and circuitry which is utilized to selectively gate that device only during one positive half cycle following the closing of the switch. A second gate controlled conduction device is utilized to discharge a capacitor in timed relationship with the alternating current potential source and prevent recharging of that capacitor until the switch is opened and then closed again.

Abstract: An optically coupled solid state relay circuit is disclosed. A light emitting diode input circuit is utilized to trigger a photosensitive transistor. A trim resistor in the base of the photosensitive transistor is utilized to adjust the sensitivity of the circuit. The photosensitive transistor is utilized, in conjunction with other circuitry, to control a silicon controlled rectifier which provides gate drive to a triac. Voltage limiting circuitry is provided to insure that the solid state relay will switch only during those periods within a selected range of the zero crossing of the line voltage and half of the bridge circuit which provides single polarity operating voltages is comprised of fast recovery diodes to improve the circuit's ability to withstand rapid polarity reversals.

Abstract: A triac device includes a first silicon chip having regions of alternate conductivity type disposed in a PN-junction forming relationship which defines a center-fired triac. A second silicon chip having regions defining a diac is bonded to the gate region of the triac chip. A copper layer of about 1 to 5 mils in thickness is bonded to the portions of the top major face of the triac chip that surround the gate region. Cathode, anode and gate connections are provided to the two-chip subassembly which is then encapsulated. The copper layer permits a smaller cathode connection to be made to the top of the triac chip without reducing the current capacity of the device.The triac device is mass-produced by first forming a plurality of triac chips in a two-dimensional array in a large area silicon wafer. The copper layers and diac chips are formed on the wafer prior to its separation into separate diac-triac chip subassemblies.

Abstract: Circuitry for applying electrical power to one or more load devices under control of a remotely located manually operable switch coupled to the circuitry by a single power transmission line. The circuitry responds to toggling of the remotely located switch to, for example, in a first state apply power to a first load, in a second state apply power to the second load, and in a third state apply power to both the first and second loads.

Abstract: A pulse transformer having primary and secondary windings on separate insulating bobbins which are carried on the arms of a pair of U-shaped ferrite cores which provide a continuous magnetic path for coupling relatively high energy pulses. The bobbin and core assembly is assembled in and held together by a close fitting molded plastic housing which carries four pins to which the primary and secondary windings are attached. The connecting pins extend from a side of the housing which is open to receive the bobbin/core assembly and are adapted for printed circuit board mounting in which the board covers the housing opening so that the transformer is completely protected.

Abstract: An improved compact electronic switch for controlling an electric motor comprising a housing into which a trigger actuator reciprocates for selecting motor speed and a reversing switch mounted on the housing and interlocked with the trigger actuator for selecting motor direction. Improvements include; an improved switch contact arrangement which reduces arcing on switching from full power to variable power motor control, an improved printed variable resistor for the electronic speed control circuitry, and an improved and simplified reversing switch unit.

Abstract: An electronic display having a plurality of digit positions is employed in conjunction with a keyboard to enter data for controlling the operation of a microwave oven. Each digit position of the display is individually responsive to a corresponding key of the keyboard, whereby actuating such key causes its display digit to run repetitively through a numerical sequence without carrying over into other display digits. Upon stopping actuation of such key, its display digit stops on the numeral displayed at that moment. Other digits of the display may be similarly loaded with data, whereby the fully loaded display represents a control parameter, such as cooking time. Actuating a start key permits the oven to carry out a cooking program in accordance with the data thus entered into the display.

Abstract: A power supply for providing two different DC voltages from a transformer having a center tapped secondary winding is disclosed. An arrangement of diodes and capacitators forming a voltage doubler is connected to the secondary winding to provide a low DC voltage from the center tap approximately equal to one half of the RMS voltage across the secondary winding, and a higher DC voltage greater than twice the RMS value of the AC voltage across the secondary winding of the transformer.

Abstract: Circuitry for converting the nominally 600 hertz output of a gasoline engine driven magneto to 60 hertz. A pair of oppositely poled controllably enabled full wave rectifiers is connected to the magneto and the load. A zero crossing detector is coupled between the magneto and a counter. A rectifier control circuit is responsive to the counter output for controlling which of the full wave rectifiers is enabled.

Abstract: A potentiometer and switch assembly wherein the potentiometer resistance is deposited on a circuit board. The control member of the assembly comprises a shaft having a rotor mounted thereon, attached to which is a wiper for contacting the resistance. The switch mechanism includes a cam shaft adapted to be engaged by the rotor whenever the control shaft is pushed. The cam shaft is positioned to the side of the rotor and is rotated through a predetermined angle each time the control shaft is pushed. Camming surfaces on the cam shaft contact one member of the switch contact pair to alternately cause that contact pair member to open and close the switch. The cam shaft may be arranged to contact a second switch contact pair which opens and closes oppositely to the first switch contact pair so that a three-way switching function may be effectuated.

Abstract: Circuitry operating as a time delay/holding relay whereby a connection is established between a pair of output terminals whenever power is applied between input terminals and for a timed period after the receipt of a predetermined signal. A first integrated circuit is connected as a free running multivibrator to generate a pulse train for maintaining a bilateral thyristor in its conductive state to close the connection. A second integrated circuit, identical to the first, is utilized to enable the first integrated circuit. The second integrated circuit is connected as a free running multivibrator but oscillations are disabled until the receipt of the predetermined signal. This maintains the enabling signal for the specified time period after the signal is received. External connections of components to the second integrated circuit changes the internal operation of that circuit.