All door hardware is connected directly to intelligent or semi-intelligent readers. Readers usually do not make access decisions, and forward all requests to the main controller. Only if the connection to the main controller is unavailable, the readers use their internal database to make access decisions and record events. Semi-intelligent reader that have no database and cannot function without the main controller should be used only in areas that do not require high security.
Main controllers usually support from 16 to 64 readers. All advantages and disadvantages are the same as the ones listed in the second paragraph.
Access control systems using serial controllers and terminal servers4. Serial controllers with terminal servers. In spite of the rapid development and increasing use of computer networks, access control manufacturers remained conservative and did not rush to introduce network-enabled products.
When pressed for solutions with network connectivity, many chose the option requiring less efforts: addition of a terminal server, a device that converts serial data for transmission via LAN or WAN. Terminal servers manufactured by Lantronix and Tibbo Technology are popular in the security industry. Advantages:
Allows utilizing existing network infrastructure for connecting separate segments of the system. Provides convenient solution in cases when installation of an RS-485 line would be difficult or impossible. Increases complexity of the system. Creates additional work for installers: usually terminal servers have to be configured independently, not through the interface of the access control software.
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