Design and Implementation of Home Intercom and Security Control Systems for Buildings

As building sizes are becoming larger and the efficiency and reliability of home intercommunication is becoming a bigger challenge, the home intercom and security systems for buildings need to be redesigned. There are several designs for home intercom and security systems for buildings, such as a traditional analog system, an industry network, a PSTN network, an Ethernet or a wireless LAN. The communication signals are transmitted digitally which facilitates various kinds of processing. Hence in this paper we propose an industry network communication system with a low-cost, simple architecture and a high-stability solution for a home intercom serving more than a thousand users in a building. As home intercom and security communication systems can be divided into talk-back, image monitors and security monitors, we only need to use those layers consisting of an OSI/ISO standard covering an application layer, a data link layer and a physical layer. We have adopted the RS-485 communication network whose wire connections have the advantage of low-cost and easy building. To achieve real-time service and avoid waste of resources we adopt the structure of mixing Peer to Peer and Master and Slave to fulfil the specification requirements. The structure of the packet includes start byte, body and stop byte. The data link layer can use back-off, control frame and a policy-based network to obtain the right to use the transmission medium for sending data.