A CIRCUIT FOR AUTOMATICALLY SWITCHING OFF POWER SUPPLY TO A RADIO OR TELEVISION WHEN THE TUNED SIGNAL GOES OFF THE AIR OR IS INTERRUPTED AND A RADIO OR TELEVISION HAVING THE SAME

摘要

A circuit for automatically switching off power supply to a radio or television when the tuned signal goes off the air or is interrupted comprising a 2-pole-3-position switch connectable to a power supply source a first semiconductor device input terminal whereof is connected to one of the poles of the said switch, output terminal whereof is connectable to the radio or television circuit and control terminal whereof is connected to the other pole of the said switch, a first resistance one end whereof is connected to the on-position contact of the pole which is connected to the control terminal of the first semiconductor device and the other end whereof is earthed, a second semiconductor device output terminal whereof is connected to the "auto off" position contact of the pole which is connected to the control terminal of the first semiconductor device, and input terminal whereof is earthed, a third semiconductor device output terminal whereof is connected to the control terminal of the second semiconductor device and input terminal whereof is earthed, a second resistance one end whereof is connected to the control terminal of the third semiconductor device and the other end whereof is connectable to a signal sensing circuit and a third resistance one end whereof is connected to the output terminal of the first semiconductor device and the other end whereof a connected to the junction of the control terminal of the second semiconductor device and the output terminal of the third semiconductor device.