Lucent Technologies Inc.

At+t Corp.

Craig Brian Ziemer

Dean Michael Umberger

Eric William Tappert

A pixel array driver for applying gray level voltages to a group of pixels without the use of a ramp voltage generator employs an integrated circuit arrangement which multiplexes a plurality of discrete gray level voltages in staircase fashion onto a high-voltage bus, identifies each of the discrete voltages appearing on the high-voltage bus with a code word applied to a code word bus, and matches for each pixel the word on the code word bus to a previously stored data word that designates the gray level intensity voltage desired at the pixel. When the code word and the data word match, the pixel is disconnected from the high-voltage bus. Each pixel is provided with a sample and hold circuit to maintain the value of voltage reached after being disconnected from the high-voltage bus.

Gray shade driver for pixel array

An integrated ringing signal detector sufficiently small for implementation on a single PCMCIA card. The detector has a DC-blocking capacitor 28 disposed between the telephone line and a bridge rectifier 27. The output 29 of the rectifier 27 connects to a voltage detector 23 which detects when the ringing signal exceeds a predetermined voltage. Output 30 of the voltage detector 23 triggers thyristor switch 24 into conduction. Switch 24 remains conductive until current flowing therein falls below the holding current of the thyristor switch 24. Current limiter 25 limits the current flowing therein to a substantially fixed predetermined amount of current, sufficient for the adequate operation of the LED in the opto-coupler transducer 22. The transducer 22 is shown here as an opto-coupler having an LED transmitter and a phototransistor receiver to provide galvanic (high-voltage) isolation between the telephone line and the utilization device, here a modem.

Telephone ringing signal detector

A high sensitivity control circuit for a solid-state relay is disclosed for use in optically coupled solid state relay circuits having a light emitting diode. The control circuit reduces a loading effect of the turn-off circuit on a photodiode array allowing the photodiode array to operate the switching transistor to switch an input signal to a switching contact. A two stage CMOS transistor circuit acting as an amplifier is employed for high-speed switching. Deactivation of the light emitting diode reverse biases a sense photodiode to discharge the switching transistor to prevent switching of the input signal to the switching contact.

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New Holland, PA, United States of America

Craig Brian Ziemer