Picture-in-picture television receivers

Claim 1

A television receiver comprising: (a) a video picture display device (18) having a picture screen which is divisible into a main picture screen (Sm) for displaying a picture represented by a first video signal and one or more sub-­picture screens (Ss) inset into the main picture screen (Sm) for displaying a compressed picture represented by a second video signal; (b) a main picture circuit (7M, 8M) for selecting the first video signal from a plurality of video signals supplied by external sources (V1, V2, V3, 5M) and supplying the selected first video signal as the main picture screen video signal; (c) a sub-picture circuit (7S, 25, 8S) for selecting the second video signal from a plurality of video signals supplied by external sources (V1, V2, V3, 5S) and supplying the selected second video signal as a sub-picture video signal for one or more of the sub-­picture screens; (d) a composing circuit (9) for composing the first and second video signals into a composite signal to be supplied to the picture display device (18); (e) a first adder (19M, 17) for adding a first picture discrimination character signal to the first video signal whereby a first picture discrimination character is displayed as part of the picture on the main picture screen (Sm); (f) a second adder (19S, 11) for adding a second picture discrimination character signal to the second video signal whereby a second picture discrimination character is displayed as part of the picture on the sub-picture screen (Ss); and (g) size control means (20, 192) for controlling the size of the second picture discrimination character as it is displayed on the sub-­picture screen (Ss).