Airport Communication Navigation Dual-Network Mutual Backup System Switching Equipment

In some important remote dispatch and control sites (such as subways, airports, military), high system reliability is often required, and services are frequently transmitted over two or more networks, with user terminals able to automatically select the normal transmission network and channel. This requires us to provide an automatic service switching system that features high reliability, strong maintainability, and the ability to accept independent control from network management systems of several networks, as well as automatic switching based on service interface status. Therefore, the switching equipment is required to use as few active components as possible to reduce the failure rate of the switching equipment itself, and to have multi-network switching interlock functionality!

Common methods to enhance system reliability include dual-interface (such as dual optical ports, or optical/electrical mutual backup) mutual backup, dual-board mutual backup, dual-unit mutual backup, and dual-network mutual backup. Dual-board mutual backup is mostly used inside equipment, such as dual power boards, dual main control boards, etc.; dual-unit mutual backup includes cold standby and hot standby; dual-network backup means each service is transmitted through two networks, and the receiving end selects the better one, usually requiring the user interface to complete selection through a selection switching device.

Common user service interfaces include Ethernet interfaces, narrowband data ports such as V.24/V.35/RS422/RS485, audio interfaces, telephone interfaces, etc. To achieve optimal selection switching and manual forced switching of user ports, different types of interfaces require different handling methods.

For Ethernet interfaces, the method of simultaneous transmission and reception over dual networks is typically adopted. When one network fails, the bandwidth is automatically reduced by half. Switching of narrowband data usually involves sending the same content simultaneously over both networks, with the receiving end automatically receiving data from the first network that has data. For these data channels, line bit errors are not considered; when bit errors occur on the line, a switching command is issued through the network management system. For voice channels, the signaling status is prioritized for judgment; when signaling status is the same, it is determined whether voice data is present. If both signaling and data are identical, the default network is preferred. These judgments are typically implemented on digital lines.