Abstract: A method of coding a ROM from a partially processed semiconductor wafer comprising a substrate, a plurality of spaced regions separated by regions of isolating oxide deposited in said substrate, a layer of gate oxide overlying each of said spaced regions and a gate electrode overlying each layer of said gate oxide, is described comprising the use of photoresist material for preventing the formation of source and drain regions under selected ones of said gate electrodes during a subsequent doping step. The photoresist material restricts the area of implantation of dopant used for forming source and drain regions in the ROM device.

Abstract: A circuit arrangement for use in telephone instruments which require battery backup for memory retention and microprocessor operation during such procedures as pulse dial address signalling where no power can be supplied by the telephone subscriber's line. Bipolar solid state circuitry may be used to provide the necessary backup power supply during these periods.

Abstract: A circuit providing a message waiting indication using a light emitting diode and a constant current surge protected circuit for use with PABX extension telephone instruments. Recently developed light emitting diodes operated with current of one milliampere or less are effectively used in the present circuitry which limits current to the device in the operating mode and also as low leakage current while in the "off" mode.

Abstract: A disconnect circuit for use between two switching systems. An optical coupler monitors open and closed current loop conditions and provides signals representative thereof. Monostable multivibrators are operated in response to these signals to provide timing signals of predetermined durations. A relay circuit is controlled by these timing signals and it operates to disconnect the loop between the switching systems for a predetermined time.

Abstract: A temperature compensated voltage reference circuit adapted for on chip location with integrated bi-polar linear circuits, where a temperature stable reference voltage is required in the range of 1.2 to 2.0 volts DC. The circuitry requires only a low chip area and presents a high AC impedance, a low operating current drain, and requires no high value resistors or capacitors.

Abstract: A fast response electronic switch used for control of connect and disconnect functions, primarily related to speech network applications for electronic-microprocessor based telephones utilizing dual tone multifrequency and/or universal pulse dial address signaling. Disclosed circuitry includes an active surge protector, a saturated transistor switch and bias circuit which exhibits a high AC impedance with respect to the telephone subscriber line.

Abstract: A test fixture including deflectable test probes employing flexible members attaching a probe head to a probe shaft, the probe head engaging a locating aperture to deflect the probe head to a printed wiring board test point not in alignment with the test probe axis. The test probe head may be of conical shape and include a plurality of ribs spaced along an outer surface thereof to reduce friction. The probe head may include a tip which is rounded to reduce test point damage or optionally pointed to achieve fine test point contacting resolution.

Abstract: A control circuit, for use in a telephone switching system, which monitors, controls and transfers data to and from memory, input-output devices and external circuits. A pair of microprocessors and associated read-only and random-access memories are operated in a master-slave arrangement. A comparison circuit continuously monitors the integrity of the master microprocessor by comparing the signal on its data, address and control leads with those of a slave microprocessor.

Abstract: A power distribution system that provides supervision and protection. Hall effect devices are used to monitor power from a central power supply to a plurality of power converters. Fuses are connected between the converters and the central power source to protect the converters from catastrophic failure. Hall effect devices also monitor the output of power from the converters. A current controlling inductor is included between the converter outputs and the output power bus in order to restrict reverse current flow from a time that is sufficient to allow a circuit breaker to disconnect a failed converter. The Hall effect devices are connected to a computer which monitors the power in and out of the converters. The computer is thus able to detect a failed converter and disconnects it by operating an associated circuit breaker.

Abstract: A control circuit which monitors the output voltage of multiple power supplies connected to each other in a diode-or arrangement. When one power supply provides a higher voltage than the others the control circuit causes the lower output power supplies to operate in a standby mode. The control circuit includes voltage dividers on both sides of the output diode of the power supplies. These voltage dividers provide indications of the voltage output of their associated power supply and the other power supplies. A voltage comparator monitors the output voltage of its associated power supply and the other diode-or connected power supplies as indicated by the voltage dividers. The voltage comparator to adjust the voltage output of the associated power supply to a level just below the high output power supply, thereby leaving it in a standby mode of operation.

Abstract: An electrical circuit functioning as a temperature sensor which is fully compatible with silicon chip and similar integrated circuit technology. Four matched NPN bi-polar transistors provide a circuit that detects changes in temperature by monitoring the current throughput in operation. Environmental temperatures increase current approximately one order of magnitude for each 25 degrees centigrade of changing temperature. With a current gain of 100 for each transistor employed, the current increases from 0.1 microamp at 0 degrees centigrade to 11 microamps at 50 degrees centigrade.

Abstract: A bidirectional word length converter for use in transferring data between a first data processing unit and second data processing unit each using a word format of a different length. The converter includes a buffer connected between the first and second units and a converter control. The converter control is adapted to accept a plurality of mode signals from the first unit to control the transfer of data in a first length word format from the first unit to the second unit in a second length word format. The converter control is further adapted to accept an alternative plurality of mode signals to transfer data from the second unit to the first unit in a similar manner.

Abstract: A support for a vertically oriented equipment drawer including a plurality of guide rollers and a band roller attached to a lower edge thereof, the guide roller riding in a lower guide track positioned on a supporting equipment floor and the band roller rolling on a band of flexible material layed out in the path of the roller as the equipment drawer is withdrawn from an equipment frame. A tensile force is applied to the band to take up slack and optionally to exert a force on the band roller to permit the equipment drawer to automatically retract back into the equipment frame. A latch is included to engage the band when the equipment drawer is in a withdrawn position to prevent automatic retraction of the equipment drawer. Flat guide rollers engaging an upper guide track are attached to an upper edge of the equipment drawer to prevent lateral movement thereof.

Abstract: A clamp for cables passing through a panel near an edge thereof including an anvil, a clamping pad and a latch member all positioned on a slideable basis within a slot extending from an edge of the panel inward a predetermined distance. Slots in the anvil interferingly engage and hold cables therein to facilitate assembly of the clamp. Fingers extending from arms of the latch member engage catches in side edges of the slot to lock the latch member in compressive engagement with the pad thereby clamping the cables between the anvil and the pad.

Abstract: A retainer for printed wiring boards mounted in a file including an open front face through which the printed wiring boards are inserted. A plurality of clips are clipped to a front support bar supporting a lower edge of the printed wiring boards and extending between a front end of a pair of support arms. The clips are arranged for sliding nonrotational movement along the support bar and each includes a retainer slot in which a retainer bar is positioned to engage a front edge of each of the printed wiring boards thereby to prevent their removal. Each clip includes a cavity which may be slid into engagement with a foot portion of the retainer bar to lock the bar in position and prevent unintentional dislodging of the retainer bar.

Abstract: An adaptor base for a telephone instrument that facilitates the instrument's use in both desk and wall mounted modes. Simplified construction allows the telephone user to reposition the base from one position to another, and even back to the first position if desired. The adaptor base is also so designed that the base and associated telephone can be mounted on a standard jack for a wall mounted telephone.

Abstract: A precise temperature dependent voltage reference and voltage comparator comprising a three terminal circuit. When the input voltage exceeds a predetermined threshold, the output switches from the nonconducting, "off" state to a current conducting "on" state. The threshold condition can be tailored to a specific temperature characteristic and low voltage range with an input current on the order of 25 microamperes. With the output tied to the input, the circuitry can act as a reference diode.

Abstract: A circuit which prevents a telephone station from being used for unauthorized toll calls while allowing toll calls to be made when preceded by authorized passwords. When the telephone station is in the toll restriction mode of operation a microprocessor disconnects the tone generator from the keypad and provides audible and visual error signals upon detection of operation of the "0" or "1" keypad buttons. Upon detection of simultaneous operation of the "1" and "2" keypad buttons, the microprocessor provides audible and visual signals to prompt entry of a password. If a valid password is entered, the telephone station enters the unrestricted mode of operation and the toll restriction circuit is disabled until the handset is returned to the on-hook position after termination of the subsequent toll call.

Abstract: A voltage comparator with both analog and digital outputs. The analog output being useful to control a analog processer such as a voltage regulator while the digital output gives an indication of the controlled state. The present circuitry may be adapted as a lowcost means of adding microprocessor control to an ongoing process whose behavior is dependent upon the state of another parameter such as the voltage exhibited by a non-rechargeable battery supply.