Abstract: A fan control system includes an AC power supply, a fan module, a switch control module, a switch unit, and a control module. The control module includes a number of outputs. The switch unit includes a number of switches. The switch control module includes a number of relays. The control module outputs a high voltage or a low voltage to control the number of relays via the number of switches to change a rotating speed of the fan module.

Abstract: A power source switching circuit, includes a first and second contact, a first, second, and third relay. The first contact includes a first normally open main contact and a first normally closed auxiliary contact. The second contact includes a second normally open main contact and a second normally closed auxiliary contact. The first, second, third normally open contacts of the first, second, third relays, connected in series, are connected between three phrase lines of the main power source and the second normally closed auxiliary contact. The second normally closed auxiliary contact is connected to a zero line of the main power source. The first, second, third normally closed contacts, connected in parallel, are connected between three phrase lines of the auxiliary power source and the first normally closed auxiliary contact. The first normally closed auxiliary contact is connected to a zero line of the auxiliary power source.

Abstract: A power supply system includes an illumination circuit for receiving an AC voltage and a control circuit for receiving a DC voltage. The illumination circuit includes a first switch unit and at least one light emitting unit. The control circuit includes a first winding unit, a second switch unit, and a second winding unit. The second winding unit provides the DC voltage to the first winding unit by the second switch unit. The first winding unit provides the AC voltage to the light emitting unit by the first switch unit. The light emitting unit emits light when receives the AC voltage.

Abstract: A three-phase power control apparatus includes a first circuit breaker, a power supply controller, and a three-phase power monitor. When the three-phase power monitor detects an error in three phase voltages provided by a three-phase power supply, the three-phase power monitor transmits a voltage signal to the power supply controller. When the power supply controller receives the voltage signal from the three-phase power monitor, the power supply controller controls the first circuit breaker to disconnect a load from the three-phase power supply. A three-phase power control method is also provided.

Abstract: A fan control system includes an AC power supply, a fan module, a switch control module, a switch unit, and a control module. The control module includes a number of outputs. The switch unit includes a number of switches. The switch control module includes a number of relays. The control module outputs a high voltage or a low voltage to control the number of relays via the number of switches to change a rotating speed of the fan module.

Abstract: A fire alarm apparatus includes a fire detection sensor, an alarm signal generator, and an isolation circuit. The isolation circuit isolates the fire detection sensor from the alarm signal generator. When the fire detection sensor detects an occurrence of fire, the fire detection sensor transmits a voltage signal to the isolation circuit. The isolation circuit transmits a trigger signal to the alarm signal generator in response to receiving the voltage signal. The alarm signal generator generates a fire alarm signal in response to receiving the trigger signal. A fire alarm method is also provided.

Abstract: A power source switching circuit, includes a first and second contact, a first, second, and third relay. The first contact includes a first normally open main contact and a first normally closed auxiliary contact. The second contact includes a second normally open main contact and a second normally closed auxiliary contact. The first, second, third normally open contacts of the first, second, third relays, connected in series, are connected between three phrase lines of the main power source and the second normally closed auxiliary contact. The second normally closed auxiliary contact is connected to a zero line of the main power source. The first, second, third normally closed contacts, connected in parallel, are connected between three phrase lines of the auxiliary power source and the first normally closed auxiliary contact. The first normally closed auxiliary contact is connected to a zero line of the auxiliary power source.

Abstract: A fan control system includes an alternative current (A/C) source, a programmable logical controller (PLC), a switch module, and a fan module. The PLC includes a detecting module. The switch module is connected to the A/C source. The fan module is connected to the switch module. The fan module includes a plurality of fans. The PLC is adapted to control the switch module thereby changing a power level output to the fan module, according to an ambient temperature of the fan module and an air pressure difference between a cold channel and a hot channel of the fan module in turn. If the pressure difference is smaller than a predefined value, the plurality of switches are switched by the PLC to provide a higher power to the fan module.

Abstract: A power supply system includes an illumination circuit for receiving an AC voltage and a control circuit for receiving a DC voltage. The illumination circuit includes a first switch unit and at least one light emitting unit. The control circuit includes a first winding unit, a second switch unit, and a second winding unit. The second winding unit provides the DC voltage to the first winding unit by the second switch unit. The first winding unit provides the AC voltage to the light emitting unit by the first switch unit. The light emitting unit emits light when receives the AC voltage.

Abstract: A system includes an alternating current (AC) power supply for supplying AC power to at least one load circuit; and a backup power supply connected to the AC power supply. The backup power supply includes a filtering and voltage-stabilizing circuit and a charge circuit. When the AC power supply supplies AC power to the at least one load circuit, the filtering and voltage-stabilizing circuit filters the AC power and stabilizes the AC power before sending the filtered and stabilized AC power to the at least one load circuit, and the charge circuit is in a charged state and stores electric power. When the AC power supply is shut off and supplies no power, the filtering and voltage-stabilizing circuit is powered off and stops operating, and the charge circuit is in a discharged state and supplies electric power to the at least one electric load.