A power supply device for supplying power to a communication device includes a power source, a first fuse, a second fuse, a voltage converter, a photo coupler, and a central processing unit (CPU). The voltage converter is configured for receiving first power signals from the power source via the first fuse and the second fuse, and converting the first power signals to second power signals. The photo coupler connected in parallel to the third resistor, configured for outputting a first electrical signal upon the condition that the first fuse and the second fuse are operational, and outputting a second electrical signal upon the condition that at least one of the first fuse and the second fuse is blown. The CPU is connected to the photo coupler, configured for generating an alarm message upon receiving the second electrical signal from the photo coupler.