Patent ID: 8227934

Claim:
A monitoring system, comprising: a controller comprising a plurality of input terminals, a plurality of output terminals, and a plurality of control terminals; a plurality of digital sensors; a plurality of analog sensors; a plurality of input devices, wherein a sum of the plurality of digital sensors and the plurality of analog sensors is equal to a number of the plurality of input terminals of the controller, each input device comprises a switching circuit, an input circuit, and a connector, the connector is connected to one of the plurality of digital sensors or connected to one of the plurality of analog sensors and a first power source in series, the switching circuit comprises an n-channel metal-oxide-semiconductor field effect transistor (MOSFET), a p-channel MOSFET, a first resistor, and a second resistor, a drain of the n-channel MOSFET is connected to a second power source via the first resistor, a gate of the n-channel MOSFET is connected to the control terminal of the controller, a source of the n-channel MOSFET is grounded, a gate of the p-channel MOSFET is connected to the drain of the n-channel MOSFET, a source of the p-channel MOSFET is connected to the second power source, a first terminal of the second resistor is connected to a drain of the p-channel MOSFET and connected to a first terminal of the connector, a second terminal of the second resistor is connected to a second terminal of the connector and grounded, the input circuit comprises an operational amplifier and a third resistor, a non-inverting input of the operational amplifier is connected to a node between the second resistor and the first terminal of the connector, an inverting input of the operational amplifier is connected to an output of the operational amplifier via the third resistor, the output of the operational amplifier is also connected to the input terminal of the controller; a plurality of alarms connected to some of the plurality of output terminals of the controller, wherein a number of the plurality of alarms is equal to the number of the plurality of digital sensors; and a plurality of displays connected to others of the plurality of output terminals of the controller, wherein a number of the plurality of displays is equal to the number of the plurality of analog sensors.