International Business Machines Corporation

David E Conner

Charles R Hoffman

Alexander G MacInnis

Lee C Haas

Paul Abramson

Melvin T Laakso

Larry A Blue

Described is an electro/optical system for transmitting video information. The system includes a transmitter assembly interconnected via a fiber optic assembly to a receiver assembly. The transmitter assembly includes a circuit arrangement which generates a data stream of analog signals interspersed with control pulses. The data stream is transmitted through the fiber optic assembly. Changes in the control pulses are detected at the receiver and are used to adjust the gain of a video amplifier.

Analog video fiber optic link

The multiplexing circuit disclosed herein combines multiple input signals into a common output by allowing ternary signals to pass from multiple input circuits to a common output circuit. The circuit combines ternary signals with minimum feedback between input circuits. The circuit is passive, has minimum attenuation, and a small number of components.

Ternary signal multiplexor circuit

A plurality of signal coupling transformers and a plurality of solid state switches are used to insert and/or de-insert data terminal equipment (DTE) from a communications network. The solid state switches are controlled to short the output of selected transformers thereby allowing signals on the communications network to bypass the DTE and/or to be switched into the DTE. The DTE may also loop electrical signals from its output to its input.

Transformer coupled, solid state communications line switch

A switching regulator causes a supply voltage to be intermittently chopped to provide energy pulses in a lowpass filter circuit. The lowpass filter circuit includes a capacitor which is being charged by the chopped energy pulses and whose output is used to drive a low voltage stepper motor. The duty cycle of the energy pulses is a function of the average value of the stepper motor coil current. By correlating the duty cycle of the energy pulses with the average current in the motor coil a relatively high torque is provided to drive the motor during a startup phase and is automatically adjusted to meet the running requirements of the particular stepper motor.

Current controlled motor drive circuit

A polling system includes a central processor and a plurality of subsystems connected in a loop to the central processor. A receive/bypass circuit in each subsystem includes a depletion mode field effect transistor having its drain and source electrodes connected in series in a bypass line at the subsystem. A control circuit is connected to a polling signal input line at each subsystem. When the subsystem has power, the control circuit routes the polling signal to a terminal device in the subsystem while establishing a conduction-inhibiting voltage at the gate electrode of the field effect transistor. When the subsystem is unpowered or out of service, a switching transistor in the control circuit isolates the terminal device from the polling signal input line. The polling signal bypasses an unpowered subsystem through the unbiased field effect transistor in the bypass line.

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Cary, NC, United States of America

David E Conner