In the prior art, the technology of converting voices into IP packages is very mature, the price of an ARM microprocessor serving as a core element of a phone gateway is greatly reduced due to development of the integrated circuit (Ic) technology, and technical conditions are prepared for practical use of the phone gateway. The VoIP technology develops from a PC primary product which limits the internal IP network range and only has voice service to telecom service which has multiple services, high reliability, good service quality and voice, fax and data transmission functions. According to a domestic intelligent network built through the phone gateway, a PSTN serves as an alarm output interface of a local user, the phone gateway and a door phone are connected through an IP network, the combination of the phone gateway and a phone replaces an indoor unit, cost of a domestic intelligent system is greatly reduced, and meanwhile, safety and concealment of the system are improved.