Picture-in-picture television receiver

Claim 1

A television receiver in which a sub-picture screen is provided within a main picture screen so that different pictures can be displayed on said main picture screen and the sub-picture screen, comprising: (a) main tuner means, including a switching circuit, to which either a first high frequency input or a second high frequency input are selectively supplied through the switching circuit to thereby form a main picture video signal for said main picture screen, the main tuner means including a user operable main channel selector for selecting a channel from a plurality of channels embodied in the first high frequency input; (b) sub-tuner means to which said first high frequency input is supplied to thereby form a sub-picture video signal for said sub-picture screen, the sub-tuner means including a user operable sub-channel selector for selecting a channel from a plurality of channels embodied in the first high frequency input; (c) means for generating a command signal for exchanging pictures displayed on said main and sub-picture screens; and (d) exchange means supplied with the command signal for exchanging the channel selection data of said main tuner and said sub-tuner with each other when said command signal is generated provided that said first high frequency input is then being supplied to said main tuner, but for inhibiting the exchange of the channel selection data of said main tuner and said sub-tuner and for generating a warning during a predetermined time period in order for a user to understood that the exchange is impossible if said second high frequency input is being supplied to said main tuner when the command signal is generated.