Browse Prior Art Database

TV Signal Polarity Control

IP.com Disclosure Number: IPCOM000076491D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Kreitzer, NH: AUTHOR

Abstract

This is a circuit for providing general purpose signal polarity control in a computer based TV display system.

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TV Signal Polarity Control

This is a circuit for providing general purpose signal polarity control in a computer based TV display system.

A computer based TV display system presents complex signal polarity control problems when it is necessary to accommodate both visual binary and analog- grade scale video, simultaneously with binary data obtained from a manually controlled cursor. This circuit creates a single output signal containing full-range analog grade scale video, of either normal or inverted polarity, as well as any of the four possible polarity combinations of digital binary and cursor datas, or any mixture of the analog and digital signals.

Referring to Fig. 1, there is shown a schematic diagram of the TV signal polarity control circuits. The circuit consists of a decoder 10, a gate 12, and a mixer 14. The decoder 10 operates on input signals obtained from two single- pole double-throw switches 1 and 2. The decoder output on line 11 provides the control signals utilized by gate 12 for selecting the desired combination of binary (V(B)) and cursor (V(C)) video polarities. The gated digital outputs on lines 15 and 16 are then mixed with an analog-grade scale video (V ) to form a composite output signal on line 17, which signal contains the desired polarities of each input.

Switch 1 only inverts digital-binary polarity signals, while switch 2 simultaneously inverts the relative polarities between the binary and cursor data signals.

Referring to Fig. 2, the...