Patent ID: 8508903

Claim:
A network communication device, for generating dying gasp signals to send to a central office device, comprising: a voltage detection circuit operable to detect voltage of an external power supply; a charging and discharging circuit configured and structured to be charged when the external power supply is on and discharge when the external power supply is off; a power supply circuit, connected to the charging and discharging circuit, to convert input voltage of the power supply circuit into a plurality of output voltages; a central processing unit (CPU), connected to the voltage detection circuit and the power supply circuit, comprising a dying gasp detection pin connected to the voltage detection circuit, wherein the CPU determines whether the external power supply is off according to the detected voltage, and generates dying gasp signals upon the condition that the external power supply is off; a load circuit, connected to the CPU and the power supply circuit, to work under control of the CPU; an over-heating detection circuit, to detect whether the network communication device overheats; and an over-heating protection circuit, connected to the over-heating detection circuit and the dying gasp detection pin of the CPU, to turn off the load circuit and the power supply circuit upon the condition that the network communication device overheats and to make the CPU to generate the dying gasp signals, the over-heating protection circuit comprising: a first switch element, comprising a control pole, a first pole, and a second pole, the first pole connected to the dying gasp detection pin, the second pole grounded via a first resistor, and the control pole connected to the over-heating detection circuit via a second resistor; a second switch element, comprising a control pole, a first pole, and a second pole, the control pole of the second switch element connected to the control pole of the first switch element via the second resistor and connected to the load circuit, the first pole of the second switch element receiving a first voltage, and the second pole of the second switch element grounded via a third resistor and connected to the power supply circuit; and a first capacitor, connected in parallel with the third resistor.