Abstract: The invention presented herein is directed to a remotely addressable maintenance unit (RAMU) working in conjunction with a test head at the central office for detecting and locating faults in digital subscriber loop (DSL) and/or plain old telephone system (POTS) environments. The RAMU includes circuitry for setting and resetting one or more relays for either normal or testing/maintenance mode. The present invention provides a system and method for addressing the RAMU by applying either positive or negative voltages from the tip to ground, from ring to ground, and from tip and ring to ground. In this manner, individual RAMUs can be defined/designed to respond in certain voltage levels and polarities. Accurate fault detection and sectionalization is achieved by the combination of the addressing capabilities enumerated herein, and the impedance signature designed into the RAMU, working in concert with a test head in the central office.

Abstract: The invention presented herein is directed to a battery injection and loop supervision (BILS) system and method that can be used in the DSL environment. The BILS of the present invention provides battery injection, loop supervision, and butt set operation mode detection in the DSL environment. A voltage source, detector and comparator in the BILS unit can be used to supervise the copper loop status from the central office. In addition, using the present invention, a field technician using a conventional butt set can detect battery voltage and receive an audible tone from the cooper loops in the DSL environment. Furthermore, the BILS can be implemented in accordance with two preferred embodiments, voltage sensing and current sensing. The BILS includes circuitry, working in conjunction with a shared common resource card and a conventional butt set, for testing, maintaining, and installing copper loops in the DSL environment.

Abstract: A wide band high voltage and high power amplifier is particularly useful for telephony applications. The amplifier employs a flyback converter with the capacitor storage element coupled across the line. The subscriber line is characterized in having a definite load impedance which impedance is in parallel with the storage capacitor of the flyback converter. The subscriber lines are monitored by a differential amplifier which provides a single-ended output indicative of the levels across the lines. This output is summed with the input signal to develop an error signal. The input signal to the line circuit is the particular signal of concern such as ringing, the voice signal and so on. The error signal is supplied as one input to a comparator having another input coupled to a triangular reference waveform. The output of the comparator provides a pulse width modulated waveform where the width of the pulses are indicative of the error signal.

Abstract: A digitally controlled ring signal generator includes a plurality of ring signal generating sources providing a plurality of inputs to each of a plurality of ring circuits. Each input is an a.c. signal superimposed on a d.c. bias that is greater than or equal to the peak voltage of the a.c. signal.

Abstract: A dual voltage source feed circuit arrangement for a two-wire telephone line circuit includes an auxiliary voltage source placed across the two-wire line and switchably controlled to connect the voltage source across the line to thereby supply an additional current to the line which current provides a optimum value of talk current to the line.

Abstract: An interface circuit for a subscriber line circuit employs a controllable amplifier including a switching converter. The switching converter includes a capacitor coupled across a two-wire subscriber line and supplies an auxiliary voltage to the line. The amplifier includes an input adder having an output coupled to the switching converter for controlling the magnitude of the auxiliary voltage with one input of the adder adapted to receive a feedback control signal which is developed by monitoring the voltage across the output. Another input to the adder receives line input signals for the line circuit. The amplifier is controlled in operation by an off hook detector which provides an output signal when the subscriber line goes off hook to cause the amplifier to operate and further includes ring control logic which is also coupled to the amplifier and activates the amplifier during the presence of a ring control signal.

Abstract: A telephone line circuit and system for interfacing digital exchange line circuits to a terminal interface of a switching network is disclosed. The system includes controllable active circuit impedance matching means for reducing impedance mismatch between a selected line circuit and the terminal interface. Control means controls both the active circuit impedance matching means for adjusting the effective circuit impedance to a value within a predetermined range, and the conditioning circuit gain pads for selectably adjusting the gain of a transmitted signal. Additionally, control means controls the d.c. line impedance and voltage for adjusting the effective line feed current to the subscriber loop, and provides interfaces for a plurality of line circuits to both a switching network and external processor. Supervision means provides supervision control signals to the control means and thereby permits the telephone line circuit system to provide desired telephone system functions.

Abstract: An apparatus and method of organizing line interface modules between analog subscriber lines/trunks and a digital switch with the provision for ringing signals which may be shared by a plurality of lines from a single source is described. The ringing signals are intercoupled to any line or lines and transmitted through a common metallic bus which provides immediate ringing for any line, with a shared ring-trip circuit. A software-controlled and/or programmable signal generator in combination with a novel ring-trip circuit is described wherein ringing cadence is generated by connecting the programmable signal generator to a subscriber line for the proper duration and at any desired frequency, whereby multi-frequency ringing can be accomplished under programmable control.

Abstract: A telephone line circuit including a high voltage amplifier feeds the tip and ring lines at its output. This amplifier is fed by a programmable voltage source which includes a d.c./d.c. converter and means to control the amplitude and polarity of this voltage. All the required electrical signals including d.c. feeding, speech, unsymmetrical ringing and metering pulses are provided through the high voltage amplifier. No high voltage AC switches (relay contacts) are required since the ring signal is provided through the same device (output amplifier) as the speech and d.c. signals. Means are included for minimizing the internal power dissipation by controlling the amplitude of the d.c./d.c. converter voltage. Thus d.c. offset control is achieved by slaving the d.c./d.c. converter voltage to the amplifier output voltage.

Abstract: A subscriber line interface circuit is described wherein the transverse and longitudinal termination impedances may be independently controlled; and wherein the equivalent termination impedance of a subscriber line/trunk as appears to the central office can be adjusted upward or downward from a lower resistance value, with longitudinal balance (also known as the common mode rejection) being determined by the matching of feed resistors. The foregoing interface circuit is implementable as a monolithic integrated circuit having low power dissipation, improved power bandwidth requirements, and lower voltage breakdown requirements for integrated circuits; all resulting in an improved telephone line interface circuit. Voltage feedback or current feedback may be employed in a circuit to synthesize the proper ac transverse termination impedance from a known dc resistance, for example, from the feed line resistors in a telephone line circuit.

Abstract: The present invention comprehends an improved ringing circuit particularly suitable for digital telecommunications systems wherein the energizing and de-energizing of the ring circuitry is programmably controlled to provide for either hardware or software generation of ringing cadence, dc bias polarity, dry-switching of ring relays, and other signaling voltages. Further in accordance with the invention, a digital implementation of a complete ringing circuit is achieved without the use of bulky transformers.

Abstract: A subscriber line interface circuit is described wherein current supplied to a telephone subscriber line from a shared voltage source such as a DC/DC converter is regulated thereby permitting a regulated line current to be supplied to a plurality of line circuits from a single shared voltage source. In accordance with the present invention, both the dc line feed and the ac transmission requirements of a subscriber line interface circuit for a telephone exchange are implemented in a single circuit incorporating ac and dc impedance synthesis techniques. A significant reduction in the heretofore required expensive and bulky discrete components of the subscriber line interface circuit is achieved.

Abstract: Circuit apparatus for supplying a regulated loop current to a two conductor loop telephone line includes first and second line feed resistances, each having one terminal connected to a respective terminal of the telephone line. A differential amplifier has one input connected to the first resistance and a second input connected to the second resistance in common with the resistance connections to the telephone line terminals. One of the resistances has its other terminal connected to the output of an active circuit means, which circuit operates in a feedback path to supply the desired loop current to the line resistance and therefore the telephone line. The input control signal for the active feedback circuit is derived from summing the output signal from the differential amplifier with a reference signal whose magnitude varies according to the length of the telephone line.

Abstract: A codec including an encoder section for encoding analog signals in compressed PCM (CPCM) and a decoder section for decoding CPCM information into analog signals features a single companding generator shared by the encoder and decoder sections. In the encoder section, an analog signal to be encoded is sampled periodically and the analog samples are compared with the decaying voltage of the companding generator which includes a capacitor, which is initially charge to a fixed voltage E. The capacitor is then discharge through a fixed resistance to another fixed voltage -dE, the discharge time being measured by a binary digital encoder counter from the start of the discharge until the voltage on the capacitor equals the absolute value of the given analog signal sample, at which time the count of the binary counter represents the desired compressed pulse code of the analog signal samples magnitude. Additionally, a sign bit, derived from the analog signal sample, indicates the polarity of said sample.