Abstract: A coded entry controlled device can power on a computer. A control circuit receives a power on coded entry via a keyboard and compares the input power on coded entry with an entry pre-stored in a storage circuit. The microcontroller actuates a switch circuit to power on the computer in response to a correct entry.

Abstract: A multimeter includes a switching circuit. The switching circuit includes a micro control unit (MCU), a first normally-open switch, a second normally-open switch, and an electronic switch. The first and second normally-open switches connect to the MCU. The MCU connects to the electronic switch. The electronic switch connects to a power control terminal of the multimeter. The MCU are operable to detect whether the first and second normally-open switches are both closed and accordingly control the electronic switch to turn on or off. The electronic switch outputs a control signal to the power control terminal of the multimeter to control the multimeter to power on or off.