Harris Corporation

Theodore E Chavannes

Edward J Zoiss

Thomas W Durston

Richard L Walsworth

Wayne K Wong

Steven R Coffelt

James D Eckman

George D Fleitz

An overvoltage protection circuit prevents damage to the electronic circuitry of a craftsperson's test set, in the event of accidental application of a potentially destructive high voltage to one or more leads of the test set. The test set's dial pulsing circuitry employs a power-dissipating N-channel MOSFET as the operative switching component. The protection circuit is coupled to the MOSFET and includes a power-dissipation controlled current-limiting and timing circuit, either as an electronic or thermostat-based implementation. During the dialing mode, the current path through the power MOSFET is alternately turned on and off by the test set's internal dial pulse control circuitry. At all times, the protection circuit provides instantaneous overvoltage protection and constant current limiting. If the excess voltage condition last long enough, the timing circuit regulates average current flow by alternately turning the MOSFET on and off, in a manner that limits average power dissipation in the MOSFET to less than a destructive value. Modulation of the current flow path through the MOSFET is based upon the product of its (source-drain) loop current and its drain-source voltage V.sub.DS, which depends upon the magnitude of the line voltage.

High voltage protection circuit for telephone test set

A pistol-configured, solenoid driven wire cutting and seating tool is connectable by way of a standard power cord to an AC voltage source and is used to seat and cut a wire by squeezing a trigger that operates a solenoid control circuit. The tool has a pistol-shaped grip and a generally cylindrically shaped barrel having a main barrel body and a nose portion. The solenoid has a bore adjacent to a butt region of the barrel, coextensive with a longitudinal axis of the barrel and accommodating the translation of a solenoid plunger. A solenoid plunger extension hammer extends from an end of the solenoid plunger, so that the plunger extension hammer extends into a generally annular cavity of the solenoid bore. Surrounding the solenoid plunger extension hammer is a solenoid return compression spring. A wire seating and cutting tool holder is axially translatable within the nose portion of the barrel. The tool holder receives a shaft of a wire seating and cutting tool and has a neck surrounded by a tool holder return compression spring. The solenoid control circuit includes an energizing current supply switch coupled in circuit with a power supply and the solenoid winding, and a switch control circuit, which is responsive to the operation of the trigger mechanism to render the energizing current supply switch conductive for a prescribed period of time and thereby apply an associated duration of firing current to the solenoid winding.

Electrically operated impact tool gun

A regulated power supply automatically accommodates either a positive or negative polarity connection of a power source and without regard as to whether the source is an DC or an AC source, and accommodating a wide range of input voltage sources. The power supply circuit includes a source voltage conditioning unit which includes an input fuse section, a surge protection circuit, a power switch, and a filter rectifier section, coupled in circuit between a set of external power source connection terminals and a set of output terminals from which a rectified and filtered intermediate voltage is derived. An open fuse detector alerts servicing personnel to an open condition of a user-replaceable input fuse. A DC-DC converter section includes a start up supply circuit and a primary drive winding of a power transformer connected to receive the intermediate rectified voltage from the filter rectifier of the input section. The primary drive winding is coupled to power switch MOSFETs, which drive the primary winding drive current under the control of a pulse width modulator (PWM). The outputs of plural secondary windings are rectified, filtered, and regulated. The rectified output of a selected secondary winding is monitored by way of current limiting and voltage feedback circuits to control the operation of the PWM.

Regulated power supply having wide input AC/DC voltage range

The telephone line test capability of a craftsperson's test set is supplemented by communication/interface circuitry which carries out data communications with a host central office control processor, and contains memory for storing (task assignment) information downloaded from the central office control processor. This task assignment information stored in the test set-communications unit may be coupled from the unit to an associated printer for providing a hard copy of service assignment information to the field technician. In addition to printing out the downloaded task assignment information, the printer unit contains a charging circuit which charges a rechargeable battery in the handset for powering its internal circuitry. During off-duty hours, the test set may be connected to a home dispatch unit installed in the craftsperson's home and through which the handset is coupled to a telephone link for providing off-duty communications with the central office processor without technician intervention. The home dispatch unit also contains a battery charging circuit through which the test set's internal battery is charged when the test set is coupled to the dispatch unit and communications between the central office and the test set-communication unit are not taking place.

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Thousand Oaks, CA, United States of America

Theodore E Chavannes