Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A DC to DC converter has an unregulated input and provides a pair of regulated outputs which independently provide variable power on demand to two independent loads at a substantially constant output voltage. The converter includes three major sections, the input oscillator and pulse width modulation section, the isolated negative DC regulator and the isolated positive DC regulator. Each of the DC regulators is current limited and each is provided with overvoltage protection. One of the output regulators provides improved efficiency through the use of a pair of appropriately connected catch diodes which decrease current change through a filtering inductor, and through implementation of a combined regulator preload resistor and AC pulse width modulating switching transistor drive current source. The converter is a compact modular unit having a low profile with circuit components arranged to minimize temperature instability.