Channel-selecting apparatus for multichannel receivers

Abstract

A channel-selecting apparatus in which is designed to determine the oscillation frequencies of a local oscillator and/or the tuning frequencies of a radio-frequency amplifier for all channels by varying analogue dc voltages being applied to a frequency control element such as a variable capacitance diode included in the oscillator and/or the amplifier in accordance with channel selective operation. Digital memory devices are provided each of which previously stores digital information representing the different predetermined analogue voltages assigned to all the channels being applied to the frequency control element. Digital information stored in the memory devices is read out upon selective operation of any of channel selection switches each coupled with the corresponding one of bistable multivibrators. A series of digital signals thus obtained are supplied to the frequency control element after being converted into a predetermined analogue voltage for the selected channel by a digital-to-analogue converter, whereby any of all the channels by selective operation of any of the channel selection switches can be selected. An automatic channel selection only for the channels now on the air is further effected by a function switch and a clock pulse oscillator designed to initiate the supply of shift or clock pulses to the bistable multivibrators collectively constituting a shift register upon operation of the function switch and terminate the supply upon reception of a first broadcasting wave after the function switch is manipulated.