Abstract: A remote control apparatus having a commander and a receiver. In a wireless remote control system for a television receiver having a channel command device and a responding device, the channel command device includes a channel selecting circuit for selecting one channel command from among a plurality of predetermined channel commands, a command signal generating circuit for generating a channel command signal corresponding to a selected channel command, and a channel command transmitting circuit having a speaker for transmitting the channel command signal; and the responding device includes a channel command receiving circuit having a microphone for receiving the transmitted channel command signal and a channel command discriminating circuit for discriminating the channel command signal and supplying a channel selecting signal corresponding to the discriminated channel command signal to control a tuning circuit of the television receiver.

Abstract: A remote control apparatus is constituted by a command encoding device and a command decoding device.

Abstract: A television signal detecting circuit is disclosed which has a first electric source, a second electric source (ground potential) different from the first electric source, a series circuit inserted between the first and second electric sources and consisting of a resistor and a condenser, a switching element connected in parallel with the condenser and adapted to become conductive and non-conductive in response to a synchronizing signal of the television signal, and a voltage detecting device connected to a junction point between the resistor and the condenser. The series circuit consisting of the resistor and the condenser prevents the voltage detecting device from becoming conductive when the television signal is absent and only noise is supplied, whereby the erroneous operation of responding to the noise as if it were the television signal can be prevented.