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: A self diagnostic test routine resident in firmware in a remote, programmable device for testing telephone lines diagnostically examines the operational capability of each of a plurality of prescribed signal processing functions contained within the test device, on a selected one of a `loop` (effectively continuous) basis, `automatically`--at a less than continuous but still meaningfully periodic rate, or `on-demand`--at any time requested by the user. In addition, a running log is maintained of the results of each diagnostic test, and the results of each diagnostic test are compared with a set of thresholds associated with respectively different standards of performance of the test device. As a result of this comparison, the performance capability or status of the device is classified into one of three categories: PASS, MARGINAL, or FAIL, and communicated to system maintenance personnel.

Abstract: A microprocessor-controlled voltage source selectively provides to a telephone line either a DC or an AC voltage, prescribed characteristics of which are programmably adjustable, enabling test equipment to controllably condition and test the line with essentially any desired line conditioning voltage or signal waveform. A digital-to-analog converter (DAC) provides an output voltage having an amplitude that is digitally programmable. This output voltage is available to be applied either directly or through controlled amplifier circuitry to the line. In order to generate an AC signal having both an adjustable amplitude and waveform characteristic, the output of the DAC sets the amplitude for a combination of signals from a plurality of squarewave generators having programmable frequency characteristics. The output of the combining unit is coupled to a switched capacitor filter which filters the controllably-interrupted, digitally-controllable output voltage, (e.g.

Abstract: A signal processing circuit measures the phase difference between digitally formated reference tone and telephone line signals over a prescribed number of signal periods so as to provide to an attendant processor an average value of phase differential. The reference tone and line signals are conditioned as square wave signals, and applied to a first exclusive-OR circuit and to respective divide-by-two flip-flop circuits, which produce square wave signals having a frequency which is half the frequency of the conditioned square wave signals. The output of the first exclusive-OR circuit represents the half-cycle phase difference between the two sine waves. The full-cycle square wave signals are applied to a second exclusive-OR circuit, which produces a series of pulses, each representing a respective full-cycle phase difference between the reference and line sine waves.

Abstract: A method and arrangement for measuring the resistance of a transducer which is coupled across a pair of conductors that are each coupled through separate sets of blocking diodes to a line card, these conductors possibly carrying a variable voltage. In the method and arrangement, a voltage of a first one of the conductors to ground is iteratively measured. This voltage from the first conductor to ground is tracked such that current flow is allowed through only one of the sets of blocking diodes. A value of the resistance of the transducer can then be accurately determined from the iteratively measured voltage values, since the variable voltage is taken into account by the tracking of the voltage from the first conductor to ground.

Abstract: An apparatus and method for accessing communication systems includes a microprocessor for controlling said accessing. Communication line access is accomplished by an interface with test trunk equipment and MDF shoes. Capability for generating dial pulse, DTMF and multifrequency dialing signals is included. Communications components and a test bus permit the apparatus to interface with a supervisor unit and a testing unit.