Patent ID: 8283937

Claim:
A monitoring system, comprising: a controller comprising a plurality of input and output (input/output) terminals and a plurality of control terminals; a plurality of sensors each to send out a detection signal detected by the sensor; a plurality of alarms; and a plurality of input/output devices, wherein a sum of the plurality of sensors and the plurality of alarms equals to a number of the plurality of input/output terminals of the controller, each input/output terminal of the controller is connected to one of the plurality of sensors or one of the plurality of alarms via an input/output device, each input/output device comprises an input circuit, an output circuit, and a connector comprising a first terminal and a second terminal, the output circuit is connected between the controller and the connector, the input circuit comprises a first metal-oxide-semiconductor field effect transistor (MOSFET), a second MOSFET, a voltage stabilizing diode, an operational amplifier, and an analog switch, a drain of the first MOSFET is connected to the second terminal of the connector, a source of the first MOSFET is grounded, a drain of the second MOSFET is connected to a gate of the first MOSFET and connected to a power source via a first resistor, a gate of the second MOSFET is connected to a corresponding control terminal of the controller, a source of the second MOSFET is grounded, a cathode of the voltage stabilizing diode is connected to the first terminal of connector via a second resistor and connected to the source of the first MOSFET via a third resistor, an anode of the voltage stabilizing diode is grounded, a non-inverting input of the operational amplifier is connected to the cathode of the voltage stabilizing diode, an inverting input of the operational amplifier is connected to an output of the operational amplifier, the output of the operational amplifier is connected to an input of the analog switch via a fourth resistor, an output of the analog switch is connected to a corresponding input/output terminal of the controller, a control terminal of the analog switch is connected to the control terminal of the controller; wherein the controller controls status of the input circuit and the output circuit, if the input/output device is connected to one of the plurality of alarms via the connector, the controller controls the alarm to work via the output circuit, if the input/output device is connected to one of the plurality of sensors via the connector, the sensor outputs a detection signal to the controller via the input circuit.