Abstract: A SEPIC converter having synchronous rectification, accommodating changes in the converter duty cycle, and the ringing conditions when the converter changes operation from a continuous mode to a discontinuous mode, and back. Conductive losses are significantly reduced.

Abstract: Interconnecting a messaging system (voice, facsimile, and so forth) with a PBX which provides entirely digital voice transmission and which provides high bandwidth and redundant transmission of control information between the messaging system and the PBX.

Abstract: Apparatus is provided to provide a start of frame signal for an incoming bipolar information signal wherein one binary state is alternately encoded with positive and negative level pulses, each of a given duration, and the other binary state is encoded with a zero or reference level. The apparatus responds to said bipolar signal to provide a first series of pulses indicative of positive pulses and a second series of pulses indicative of negative pulses. A clock is provided which operates at a higher frequency than the bipolar signal. Counting means are provided and are responsive to said first and second signals and said clock to provide third and fourth signals each of said signals indicative of the true polarity of the input signal transitions to enable the processing of true data as compared to noise.

Abstract: A DC to DC converter employs a single ended blocking oscillator which employs a transformer having a primary winding and a plurality of secondary windings. The transformer has a core which is of a square loop hysteresis type. The blocking oscillator is supplied operating voltage by means of a voltage regulator circuit which operates to regulate the voltage applied to the blocking oscillator according to both input voltage variations and output load variations. Due to circuit operation, the output voltage is extremely well regulated while having low ripple. An output secondary winding of the transformer is coupled to a rectifier. The rectifier output is fed back to the regulator to control the voltage applied to the blocking oscillator to cause the blocking oscillator to provide a waveform to maintain the output voltage constant.

Abstract: Apparatus generates synchronized timing for both the up and down links of a transmission path such as a telephone line, which telephone line carries bipolar data. The apparatus operates to detect a Start of Frame signal which signal constitutes a known violation in the bipolar data. This Start of Frame signal is applied to a series of dividers and decoders which operate in conjunction with an oscillator to produce a series of timing signals related to the Start of Frame signal. A selected one of the timing signals is utilized to synchronize the up link apparatus to the down link apparatus. In this manner the counter circuitry which is employed in both the down link side and the up link side is used to accumulate any timing difference between the data source and the data receiver. After a number of bit periods have passed, the timing signals generated will move with respect to a data bit, depending on whether the clock at the transmitting end is slower or faster than the clock at the receiving end.

Abstract: In a current level sensing circuit employing a gyrator to control an opto-isolator, a coupling circuit having an input impedance of a magnitude sufficiently higher than the output impedance of the gyrator that it does not substantially load the gyrator is employed to couple the gyrator output to the opto-isolator. In one embodiment, a differential amplifier receives the gyrator output at a first input which is associated with an output that is coupled to the isolator and a predetermined reference voltage supply is applied to a second input of the differential amplifier. A current sink is connected in a common load path portion of the differential amplifier and is otherwise connected to implement differential amplifier current limiting at a level which assures damage-free operation of the isolator as well as insensitivity to low amplitude electrical disturbances applied to the gyrator.

Abstract: The apparatus converts an AMI signal into three unipolar signals by selectively amplifying the AMI signals so that higher frequency components are amplified greater than lower components and then comparing the AMI signal with a positive and negative threshold to provide a first unipolar signal having information relating to positive levels of said AMI signal, a second unipolar signal having information relating to negative levels of said AMI signal and a Or gate for combining said first and second signals to provide a third signal having information related to both positive and negative levels.

Abstract: A circuit for translating bipolar signals into unipolar signals, in which the bipolar signals are applied to an amplifier whose gain is automatically controlled to produce bipolar signals of constant amplitude that are applied to two biased comparators for producing P DATA and N DATA signals of the same polarity. These signals are OR'd to provide R DATA signals.

Abstract: A DC to DC converter employs a push-pull oscillator which employs a transformer having a primary winding and a plurality of secondary windings. The transformer has a core which is of a square loop hysteresis type. The push-pull oscillator is supplied operating voltage by means of a voltage regulator circuit which operates to regulate the voltage applied to the push-pull oscillator according to both input voltage variations and output load variations. An output secondary winding of the transformer is coupled to a full wave rectifier. The full wave rectifier output is fed back to the regulator to control the voltage applied to the push-pull oscillator via the regulator. Due to circuit operation, the output voltage is extremely well regulated while having low ripple.