Zenith Radio Corporation

Walter S Ciciora

A subscription television system comprises means for broadcasting a scrambled television signal wherein the NTSC horizontal and vertical synchronization signals are displaced in time from their nominal positions. Each authorized system subscriber is provided with a decoder adapted for restoring the synchronization signals to their nominal positions to enable unscrambling of the broadcast programs for viewing. The synchronizing signals may be time displaced in a static manner or the time displacement may be dynamically varied as a function of time.

Sync displacement scrambling

An equalizer and decoder system compensating for multipath distortion in digital format signals sent by teletext, for example. The system loads demodulated data signals and a received reference signal into a charge coupled device clocked in real time by a clock circuit. Later, the reference pulse is clocked to a microprocessor which determines tap coefficients for a transversal filter to correct the multipath distortion in the reference signal. The data signals are then applied to a transversal filter weighted with the calculated tap weights. After filtering, signals are decoded by the microprocessor. In another embodiment a charge coupled device with tapped stages is used at one time for receiving the data signals in real time, and at a later time for part of a transversal filter. In a simplest embodiment, distortions are removed by the microprocessor itself, without any separate transversal filter.

Intelligent teletext decoder

A television receiver is disclosed for selectively displaying either a 525 line NTSC video signal or a 625 line European teletext or Viewdata signal. The receiver includes two vertical countdown circuits: a 525 line countdown circuit for use in generating an NTSC type raster, and a 625 line countdown circuit for use in generating a 625 line raster. Switch means are provided for selecting between the two signals generated by the countdown circuits. The receiver CRT uses self-converging, in-line guns.

Raster manipulated television receiver

A Teletext equipped NTSC television receiver system includes means for compressing the raster in the vertical direction in response to 625-line formatted Teletext signals to display normally overscanned horizontal lines on the television viewing screen. Thus 625-line formatted Teletext material may be used directly with NTSC receivers.

NTSC receiver useable with Teletext/Viewdata information

An automatic channel equalization system for use with a television receiver includes a control section for automatically operating a transversal equalizer according to the distortion exhibited by a reference signal transmitted through the channel. The television line including the transmitted reference signal is supplied to the control section through a time base expander enabling the implementation of a relatively fast sampling rate for achieving full bandwidth equalization of the channel with relatively slow-speed signal processing technology.

Automatic channel equalization with time base expansion

Patterns indicative of the characteristics of contrast, brightness, color and tint are displayed on the picture tube of the television receiver. A plurality of photocells develop corresponding electrical signals responsive to the patterns. The signals drive peak detectors, the outputs of which are sampled at a regular rate. A neutral density filter is between the brightness pattern and its photocell, and when the sampled contrast and brightness outputs are subtracted in a subtractor, a null is obtained at the desired ratio. Color filters are interposed between the tint and color patterns and photocells and at the desired settings, subtraction of their outputs in a subtractor yields zero. A plurality of bi-directional motors are engageable with the receiver contrast, tint, brightness and color level adjustable elements. The contrast and tint adjustment elements are driven from the respective subtractor outputs, whereas the brightness adjustable element is controlled by the brightness peak detector output directly and the color level adjustable element is controlled by the sum of the color and tint peak detector outputs. The motors are stopped when all patterns correspond to desired settings. The method of automatically setting up a color television receiver is also described.

Growing community of inventors

Park Ridge, IL, United States of America

Walter S Ciciora