Television system for simultaneously transmitting and receiving a

Abstract

Apparatus for transmitting and receiving a plurality of separate pictures or scenes on a single television carrier signal such that a different picture appears in each quadrant of a television receiving tube, and including means for blanking out all but one quadrant and for centering and expanding that quadrant to fill the entire screen of the receiving tube. This is accomplished by separating the sync signals from the video, followed by delaying the sync signals and recombining them with the video such that the video portion, representing one quadrant, is essentially centered between horizontal and vertical sync pulses. Expansion of the single quadrant after it is centered on the tube is achieved by increasing the amplitude of the vertical and horizontal sweep waveforms. In one embodiment of the invention, a special receiver is used for centering and expanding a quadrant; while in another embodiment, an adapter is employed which essentially demodulates an incoming signal, separates and delays the sync signals, and recombines them with the video; whereupon the altered video signal is modulated for application to the antenna terminals of a conventional receiver. The invention finds particular utility in educational television systems where a pupil, for example, is required to select a correct answer from one of four presented at the four quadrants of a receiving tube.