| 摘要 |
System to automatically switch on/off the electricity supply to a monitored area comprising a dipole aerial system, preferably comprising two parallel wires provided about one foot apart and about one inch below the floor of the monitored area, where the dipole aerial is an extension of the capacitor plates of an LC oscillator circuit (figure 2) and is such that the proximity of a person (electrical conductor) alters the frequency of the oscillator circuit. This frequency change is converted by a phase locked loop (PLL) into a voltage change which is fed into an operational amplifier wired as a Schmitt trigger. The output of this controls a transistor and relay to switch the electricity supply, e.g. lighting, on when a person is present and off when a person is not present. Electricity is conserved when the monitored area is unoccupied by switching off lighting and/or devices such as television sets, radios, etc. An independent power supply may be provided for devices requiring a permanent electricity supply, e.g. tropical fish aquarium and the system may also be used in public spaces to control street lighting. |
