Mitsubishi Denki Kabushiki Kaisha

Luma Telecom Incorporated

Mitsubishi Electronics America, Inc.

Michael A Cooper-Hart

Lawrence D Emmons

David H Stokes

James S Mackley

Seiji Wada

Takeshi Taniuchi

William E Brisko, Jr

Rudolph S Stefenel

An improved video phone which transmits a source image over a standard telephone line in conjunction with audio voice signals is disclosed. The unique initialization protocol allows asynchronous transmission with its short format. The protocol format provides for a hardware preamble for synchronizing a receiver clock, a software preamble for identifying the video image and disabling the audio, automatic gain control adjustment data and amplitude calibration data. The audio portion is disabled by coupling a capacitor across the telephone to effectively short the telephone. The telephone is placed across the bridge circuit which is provided with switches to balance the bridge in both the telephone audio and the video modes. The transmitted as well as the received signal are passed through the same delay equalization circuit, so that half the delay equalization is done before transmission, with the remaining half being done after reception. The use of a multiplexer and demultiplexer allows the same circuit to be used. The digital signals are level shifted from 5 volts to 10 volts prior to being converted into analog, and then are level shifted down again to reduce the effects of DC offset. The digital and analog voltage supplies are coupled together with a resistor and diode, and a capacitor is coupled between the analog supply and ground to combine the reset and voltage supply functions. An RC circuit providing 180.degree. of phase shift is coupled to the crystal oscillator to produce a clock which is locked into the series resonant frequency of the oscillator. The camera and the rest of the circuitry is turned on and off by a switch coupled to panel which can be slid in front of the camera, thus providing for the automatic protection of the camera lens when the system is switched off.

Conversational video phone

An improved video phone transmits a source image over a standard telephone line in conjunction with voice signals. The unique initialization protocol provides a hardware preamble for synchronizing a receiver clock, a software preamble for identifying the video image and disabling the audio, automatic gain control adjustment data and amplitude calibration data. The audio portion is disabled by coupling a capacitor across the telephone to effectively short the telephone. The telephone is placed across a bridge circuit which is provided with switches to balance the bridge in both the telephone and video modes. The transmitted and received signals pass through the same delay equalization circuit, so that half the equalization is done before transmission, with the remaining half being done after reception. Input and output selectors allow the same circuit to be used. The digital signals are level shifted up prior to being converted into analog, and then are shifted down again to reduce the effects of DC offset. The digital and analog voltage supplies are coupled together with a resistor and diode, and a capacitor is coupled between the analog supply and ground to combine the reset and voltage supply functions. An RC circuit providing 180.degree. of phase shift is coupled to the crystal oscillator to produce a clock which is locked into the series resoonant frequency of the oscillator. The camera and the rest of the circuitry are turned on and off by a switch coupled to panel which can be slid in front of the camera.

Telephone machine with TV receiver

The present invention is a conversational freeze-frame video phone which transmits a source image over a standard telephone line in conjunction with audio voice signals. A camera is used to capture an image to be transmitted and the image is mapped onto an image field of 2,000 to 5,000 pixels. The image field is displayed on a display area of approximately one square inch on a display screen. Digitized data representing the pixels is asynchronously transmitted on a modulated signal in a single burst of less than three seconds duration. Corresponding remote images are asynchronously received, demodulated, and displayed. The transmission of the audio signal is interrupted upon the detection of a video image being transmitted.

Growing community of inventors

Cupertino, CA, United States of America

Michael A Cooper-Hart