Abstract: In the safe protection net (SPN) designed, the connection of the frontage control boxes and the center control station is accomplished by the communication net. The information could be transferred on the power line in the form of digital signal, or on the telephone line by a modem with and image. It is the digital signal that especially determines the actions of alarming or some related control. So the veracity of it is the main demand to the system. In the SPN designed, some advanced methods are used to ensure the high reliability of the communication of the signals.