A circuit where a rotary push switch module with first and second switches are closed and first and second terminals of a NAND gate receive high level signals. An output terminal of the NAND gate outputs a low level signal. A light emitting diode (LED) is not lit. A voltage output terminal outputs a standby voltage. When the first switch is opened, and the second switch is closed, the first and the second input terminals of the NAND gate respectively receive a high level signal and a low level signal. The output terminal of the NAND gate outputs a high level signal. The LED is lit. The voltage output terminal does not output the standby voltage.