1. The drawback of this type of controller with its own card reader is that the controller must be installed outside the door. Therefore, some control lines must be exposed outside the door. Insiders can easily open the door without a card or password. 2. This type of system controller, in which the controller and reader are separate, is installed indoors, only the reader input line is exposed outdoors, all other control lines are indoors, and the reader transmits a digital signal, so if not No one can enter the door with a valid card or password. This type of system should be the user's first choice. The access control system can be divided into the following two categories according to the communication method with the microcomputer: 1. Stand-alone products of this type are the most common and are suitable for use with small systems or installation locations. RS485 communication is usually used. Its advantages are low investment and dedicated communication lines. The disadvantage is that once installed, the location of the management center cannot be easily replaced, and network control and off-site control are difficult to achieve. 2. The technical content of such network-type products is high, but it is rare at present, and only a few companies have formed products. Its communication method uses the commonly used TCP/IP protocol of the network. The advantage of this type of system is that the controller and the management center transmit data through the LAN. The location of the management center can be changed at any time. It is easy to implement network control or remote control without rewiring.
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