Rolm Company

Rolm Systems

Durel Corporation

Rolm Corporation

Joseph D Remson

Kenneth E Waln

Ivan M Lee

Maura E Higgins

Daniel A Harrington

An EL lamp is charged to a first polarity with a series of high voltage pulses, discharged at a controlled rate, charged to a second polarity with a series of high voltage pulses, and discharged at a controlled rate, thereby producing an alternating current through the lamp. A flyback circuit provides the high voltage pulses. The polarity of the pulses is reversed periodically at a low frequency and the EL lamp is prevented from discharging through the flyback circuit by a phase shift circuit that produces a discharge pulse in advance of each change of polarity of the high voltage pulses. The discharge pulse interrupts the high voltage pulses and discharges the EL lamp through a constant current load.

Low noise inverter for EL lamp

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. The telephone system includes: (a) a telephone switching system including an interface to one or more digital links, the interface for supplying control and voice information relating to a call over one of the digital links and for receiving other control and voice information relating to the call or to another call over the digital link, the other control and voice information relating to another call including information relating to In-Band Message Notification (IBMN); (b) a messaging system for receiving a portion of the control information and a portion of the voice information relating to the call from the telephone system and for transmitting the other control and voice information to the telephone system; and (c) a messaging system interface between the digital links and the messaging system, the messaging system interface for receiving the control and voice information from the digital link and for supplying the portion of the control information and the voice information from the call to the messaging system and for transmitting the other control and voice information received from the messaging system over the digital link.

Method and apparatus for interconnecting a messaging system and a

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. The output of the counting means are coupled to logic means whereby if two or more successive pulses of the incoming signal have the same polarity, then a start of frame signal is provided by the logic means as coupled to the counting means.

Apparatus for detecting the start of frame in bipolar transmission

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.

DC to DC converter employing a free-running single stage blocking

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. The operation causes the receiving end to synchronize with the transmitting end.

Digital phased locked loop apparatus for bipolar transmission systems

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. Circuitry for unbalancing the amplifier operation can be used to provide an hysteresis effect in the current transfer function of the amplifier.

Current level sensing circuit for use with gyrator circuitry

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.

Apparatus for converting an alternate mark inversion signal to unipolar

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.

Bipolar to unipolar converter with automatic gain control

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.

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San Jose, CA, United States of America

Joseph D Remson