| 摘要 |
The circuit switches off the electrical power supply to electrical equipment which is not actually being used. The supply would normally be from batteries for television, radio, telephone amplifiers etc., the circuit preventing unnecessary discharge if the user has forgotten to switch off the equipment. The circuit operates by sensing the output e.g. sound, from one of the items of equipment and after some given time after the disappearance of this disconnects the supply. The sensor (3) feeds an amplifier (1) whose output is taken to a loudspeaker (4) and to a four transistor amplifier and delay circuit which has a relay coil (27) load opening (28) the supply circuit in the absence of an input signal. Both circuits are powered from a battery (5) via a further relay (6, 7) initiated by a resetting push-button (8) associated with the sensor. |
