Television special effects circuit for wiping video signals

A special effects circuit for wiping from one composite video source to another composite video source comprising:

• a first variable gain linear amplifier having an input terminal for receiving video signals from a first source of composite video signals, an output terminal, and a control terminal;
• a linear inverter circuit coupled to said control input terminal of said first amplifier;
• a second variable gain linear amplifier having an input terminal for receiving video signals from a second source of composite video signals, an output terminal coupled to said output terminal of said first amplifier, and a control terminal;
• circuit means for providing a wipe control signal applied to said control input of said second amplifier and to said inverter, said control signal having a blanking interval and a video signal interval and wherein said level of color burst voltage signals during said blanking interval is directly proportional to the proportion of video being wiped whereby the color burst signals at the output of said amplifiers during said blanking interval are proportionately mixed while the video information signals are wiped from one source to another in the same proportion.

A special effects circuit for wiping from one composite video source to another composite video source comprising:

• a first variable gain linear amplifier for receiving composite video signals from one source, said amplifier having an input terminal, an output terminal, and a control terminal;
• a second variable gain linear amplifier for receiving composite video signals from another source, said second amplifier having an input terminal, an output terminal, and a control terminal;
• a variable voltage source for providing a wiping control voltage;
• an inverter coupled to said control terminal of one of said first or second amplifiers;
• first and second gate circuit means having input terminals and commonly coupled output terminals, said output terminals coupled to said inverter and to the control terminal of the other of said first or second amplifiers;
• means for applying blanking signals of opposite polarity to said gate circuits to enable one of said gates during a blanking interval and disable the other of said gate circuits during a blanking interval;
• means coupling said variable voltage source to the input of the gate enabled during a blanking interval;
• and
• wipe generator means coupled to said variable voltage source and including means for receiving horizontal and vertical drive signals for providing at an output terminal thereof, a wiping control signal, said output terminal of said wipe generator means coupled to said other gate circuit whereby a composite wiping control signal is provided to the commonly coupled output terminals of said gate circuits and applied to said first and second amplifiers to mix the color burst signals of the two video sources during each blanking inteval and to wipe from one video signal source to the other as the voltage from said variable source is varied in the same proportion.