Apparatus for receiving signals in plural frequency bands

Radio receiving apparatus for receiving signals in plural broadcast frequency bands, comprising:

• at least first and second tunable processing channels, each channel being associated with a respective frequency band and each being tunable to different frequencies within the respective band associated therewith, said first and second channels including first and second IF stages, respectively, for producing information signals, one of said IF stages being selectively operable in response to an enable signal applied thereto and also producing a control signal when the channel in which said one IF stage is included is tuned to a broadcast frequency;
• means for simultaneously tuning said at least first and second processing channels;
• switch means normally connected to one of said processing channels;
• output means coupled to said switch means to receive the information signals produced by said processing channels;
• pulse generating means operable when said means for tuning is changed for generating pulses when the tuning condition of said at least first and second processing channels is changed;
• first transistor means responsive to each generated pulse for applying an enable signal to said one IF stage;
• second transistor means responsive to said control signal produced by said one IF stage to cause said first transistor means to continue to apply an enable signal to said one IF stage even in the absence of said generated pulses;
• and
• switch drive means energized by said second transistor means to change over said switch means to connect another of said processing channels to said output means.