Abstract: A local area network for interconnecting terminals and other users and data processing systems and other service providers over a communications link by means of interface units each of which may connect to several users or providers. The interface units communicate over the communications link by means of messages. When a user requires the use of a service, the interface unit establishes a virtual circuit between it and the interface unit connected to the service provider and a service session which allows the user and the service provider to communicate over the virtual circuit. If several users connected to the one interface unit as the first user require services provided by providers which connected to the same interface unit as the first provider, they communicate in sessions over the same virtual circuits. The session messages are accumulated into single virtual circuit messages that are acknowledged in unison by the receiving interface unit.

Abstract: An electromagnetic contactor includes a housing assembly that may be adapted for one, two, three or four poles. An armature is affixed to a contact carrier either by a flat leaf spring that passes through a slot in a laminated armature or by a press fit of a solid armature into the contact carrier. In one embodiment of the invention, a housing assembly snaps into a base to permit a maximum amount of automatic asssembly and a minimum number of components. These components include a base, a magnet assembly having at least one shading coil, a formed coil assembly, two symmetrically disposed springs to return a contact carrier to a neutral position when the coil is de-energized, an armature to complete the magnetic circuit that is attached to the contact carrier, a contact block that supports terminals and stationary contacts, and a contact carrier that carries one or more moving contacts into engagement with the fixed contacts.

Abstract: A localized cooling apparatus is provided for individually cooling integrated circuit chips mounted on a circuit board for insertion into a computer backplane. The cooling apparatus consists of a circuit board occupying a first slot and having an integrated circuit chip mounted thereon, the performance of which is known to improve by cooling, a heat removal assembly consisting of a heat sink attached to a card edge portion and occupying an adjacent second slot, and a thermoelectric cooler intimately bonded to both the chip and heat removal assembly. A controller provides power via the connector of the second slot to the thermoelectric cooler and stabilizes the temperature of the chip to a predetermined value.

Abstract: The circuit operates a main switch SCR to pass an a.c. supply V through a load L when a metallic object is in proximity to coil L1. Coil L1 is driven by an oscillator comprising transistor T2 and associated components. SCR is gated on simultaneous occurrence of an output from level detector T3 and a signal from T5, these being ANDed by T4. The timing of the signal from T5 in the supply cycle is governed by the RC time constant of C4,Z1,R14 and is such that the power supplied to the oscillator and level detector is the minimum necessary, for a wide range of supply voltage and load current.

Abstract: A fiber-optic switch uses a single optical fiber for two-way communication with light. A switching mechanism has no electrical part and is thus appropriate for placement in an area having explosive or combustible materials. The optical fiber can be cut to length in the field and can be installed without special tools or training. The fiber is held in place by a clip that is constrained to compress the fiber and grip it securely. A snap-action mirror reflects light back into the fiber in one position and does not reflect it in another position. The mirror is maintained in one of the two positions by a spring force. An electronic circuit provides pulsed light and determines coincidence of sent and received pulses to discriminate against operation of the switch by ambient light or other spurious signals.

Abstract: An electric current detector has a light source for generating light having substantially linear polarization and a predetermined polarization direction, a material substantially transparent to the light, the material having at least one characteristic direction, and the material exhibiting the Faraday effect in response to a magnetic field generated by the electric current. Also the light is launched into the material, and a predetermined angle established between the polarization direction and the characteristic direction, the predetermined angle chosen to permit separation of a rotation of the polarization of the light by the Faraday effect from polarization effects on the light by a birefringence of the material. A value of 22.5.degree. for the magnitude of the predetermined angle permits a separation of the rotation of the polarization due to the Faraday effect from polarization effects due to a birefringence of the material.

Abstract: The invention provides a terminal for a coil. One embodiment of the invention is a housing made of molded insulating material: a projection molded into the housing; a lug made of electrically conductive material and having a recess therein for accepting the projection molded into the housing for preventing motion of the lug in a first direction; a support molded into the housing for supporting the lug and for preventing motion of the lug in a second direction; a lip, molded into the housing, and the lip accepts a first end of the lug for preventing motion of the first end of the lug in a third direction; and, a finger molded into the housing for securing a second end of the lug and preventing motion of the second of the lug in the third direction, thereby retaining the lug in the housing. The lug may snap under the finger. The housing may be a cup for retaining at least one coil bobbin, and there may be two coil bobbins.

Abstract: A reduced voltage starter for gradually starting a polyphase motor having an acceleration control circuit for gradually applying power to the motor and detector circuits for detecting various fault conditions for terminating power to the motor. A shorted solid state switch detector senses when one of the semiconductor switches applying power to the motor is shorted to terminate the application of power from the remaining phases. A phase angle control circuit insures a uniform application of power to the motor. A phase rotation detection circuit detects when the three phases are in other than their correct sequence and terminates power in the event of such detection. An underload detection circuit senses when the current drops beneath a preselected reference after the motor has reached its full speed and terminates power in response to such detection. A line-to-line-to-line-to-neutral convertor produces signals representative of the line-to-neutral voltages which are necessary for other circuit functions.

Abstract: A pressure sensitive switch has means for producing linear motion in response to pressure, means for springably resisting the linear motion, means for operating a switch after a predetermined linear motion, and a lifter pin having a projection on a first end for slidably engaging a hole in the means for springably resisting the linear motion, the lifter pin being mounted between the means for producing linear motion and the means for springably resisting the linear motion so as to transmit force from the means for producing linear motion to the means for springably resisting the linear motion, the lifter pin decoupling rotational motion between the means for producing linear motion and the means for springably resisting the linear motion. A piston may serve as the means for producing linear motion in response to pressure.

Abstract: The invention provides a simple optical switch capable of integration with common machine tool control devices such as push buttons, limit switches, and pressure responsive switches. The invention is an optical switch comprising a housing for mounting the optical switch, a drive rod capable of motion, and at least one mirror surface movable with the drive rod for reflecting light in a desired direction.

Abstract: A gate drive circuit for a thyristor has a power supply and an amplifier for supplying current to a gate electrode of the thyristor. A timing signal is generated to initiate conduction of the thyristor. A voltage level signal is generated in response to a voltage from cathode to anode of the thyristor to indicate a reduction in the cathode to anode voltage of the thyristor when the voltage is reduced by conduction of the thyristor. Current is supplied to the gate electrode of the thyristor in response to the timing signal, and current ceases to flow to the gate electrode of the thyristor at a predetermined time interval following generation of the voltage level signal indicative of a collapse in cathode to anode voltage of the thyristor caused by conduction of the thyristor, and the predetermined time interval is chosen to be of sufficient duration to permit conduction of the thyristor to reach a stable value before current flow to the gate electrode of the thyristor substantially ceases.

Abstract: A modular switch device includes a housing enclosing an interconnected control module, a display module and a power module. A sensor module supplying analog data signals from one of a temperature or pressure sensing element connects to the control module through a passage in the housing. A user connects his electrical wires and electrical power to the electrical assembly within the housing through an opening. The user can select between AC and DC switched output modules and the presence or absence of a 4-20 milliampere output module by plugging and unplugging same from wells provided in the housing. The manufacturer and user thus can modify the standard housing, which includes an internal electrical assembly to be a pressure or temperature switch and to provide selected output switch characteristics by applying and removing selected sensor and output modules thereto.

Abstract: A monitor for an electric motor, the monitor capable of connection to a supply of electrical energy for the motor, has a microcomputer for measuring the power factor of a voltage applied to the motor and a current flowing to the motor, for storing a desired value of power factor, for comparing a measured value of power factor with the desired value of power factor, and for disconnecting the motor from the supply of electrical energy if the measured value of the power factor differs from the desired value of power factor by an amount that exceeds a predetermined amount. Further, the monitor has means for operating the motor while driving a desired load; means for commanding the microcomputer to measure a power factor of the voltage applied to the motor and the current flowing to the motor while the motor is driving the desired load; and, means for storing the measured value of the power factor, measured while the motor is driving the desired load, as the desired power factor.

Abstract: A polyphase circuit fuse condition indicating device includes three substantially identical circuits forming a Y-connection across each fuse through first and second leads. Each circuit has an indicator light and a switch with resistors in the leads. The respective circuits are interconnected through a lead having a resistance for each circuit so that an indication will be rendered without a load across the fuse.

Abstract: A limit switch includes a housing which encloses a snap switch having first and second pairs of spaced fixed contacts and first and second movable contacts supported on a carrier and operated by first and second reciprocating plungers that are biased to a first position. Toggle springs are interposed between the respective plungers and the carrier to move the carrier and the associated contacts between fixed pairs of fixed contacts during reciprocation of the respective plungers. An actuator head is mounted on the switch housing and has cams for actuating the respective plungers.

Abstract: A transient protection circuit for an inverter has a rectifier capable of supplying direct current from an alternating current power source, where protection is provided against a voltage transient in the AC power source. A DC bus is fed by the rectifier. A bus capacitor is connected across the DC bus. Solid state switches are connected to the DC bus for supplying alternating current to a load. The DC bus voltage is sensed. In response to a transient rise in the DC bus voltage, a resistor is connected across the bus capacitor to provide a discharge path, the solid state switches are disconnected from the DC bus, and after the transient dies away from the DC bus, the solid state switches are reconnected to the bus and the discharge resistor is disconnected from across the bus capacitor.

Abstract: The inventions solves the problem of convenient mounting of parts of controllers, and solves the problem of interchangeability of vacuum and air break contactors within a controller. A controller has a housing, an isolation switch mounted within the housing, a contactor mounted within the housing and connected electrically downstream from the isolation switch, and the controller has a receptacle which can accept either a vacuum contactor or an air break contactor. Also, the contactor has an operating coil and control components mounted on a side facing a door of the housing so that the coil can be replaced and the control components serviced without disturbing the contactor.

Abstract: The invention provides a terminal for a coil. One embodiment of the invention is a housing made of molded insulating material; a projection molded into the housing; a lug made of electrically conductive material and having a recess therein for accepting the projection molded into the housing for preventing motion of the lug in a first direction; a support molded into the housing for supporting the lug and for preventing motion of the lug in a second direction; a lip, molded into the housing, and the lip accepts a first end of the lug for preventing motion of the first end of the lug in a third direction; and, a finger molded into the housing for securing a second end of the lug and preventing motion of the second of the lug in the third direction, thereby retaining the lug in the housing. The lug may snap under the finger. The housing may be a cup for retaining at least one coil bobbin, and there may be two coil bobbins.