First, what is the access control?
 The access control controller is the core data processing and storage part of the access control system, and it is the soul of the access control system. 

Second,the usual classification of access control.

(1) According to the communication mode of the controller and the management computer, it is divided into: RS485 networked access controller TCP/IP network access controller 

 RS485 networked access control controller usually also has RS232 serial port communication mode, through RS232 serial port and computer for stand-alone communication. In addition, the controller communication networking mode and Lan Longwork industrial bus mode, but these communication modes are rarely used, have advantages and disadvantages, it is not convenient for users to replace with other compatible products in the future. 

(2) According to the number of doors controlled by each controller can be divided into: single-door controller two-door controller four-door controller 

 Note: There are also eight controllers, sixteen controllers, thirty-two controllers on the market, the output is very small, manufacturers designed products for cost considerations, in fact, it is very inconvenient in the construction of wiring, must be 8 doors (16 doors, 32 doors) of the equipment are in the effective communication range to be used, and because of too many lines into the host chassis, Easy to produce interference and instability. Therefore, we believe that these products are only conceptual products, and have not entered the practical link. In fact, the number of doors controlled by the controller can not reflect the design advancement of the product, and the difficulty of increasing the input port of a four-door controller into 8 doors 16 doors 32 doors is not large, which brings negative stability effects, and the inconvenience of construction has a greater impact.  

(3) According to the number of card readers can be connected to each door, the controller is divided into: one-way controller Two-way controller 

 if a door, swipe the card at the door, go out and press the button, the controller can only be connected to one card reader for each door, we call the one-way controller. 

If a door, the door swipes the card, and the door swipes the card (you can also pick up the door button), each controller can pick up two card readers for each door, one is the door reader, one is the door reader, we call the two-way controller. 

 Note: If the two-way controller, only access the door reader, go out does not access the door reader (port idle), go out to open the door button. The equivalent of a one-way controller is also possible. Here to distinguish a "double door" concept, some doors can be opened and can be opened, called can be opened inside and outside, this has nothing to do with the classification of the access control controller. There is also the concept of "double doors", some doors, such as the glass door of the company gate, are composed of left and right doors, but each door is equipped with an electric lock, and the two locks are connected to the relay of one door on a controller. Instead of using a double door controller, a single door controller can control the double door. 

 The access controller is divided into two categories according to the communication mode. 

 The first type supports RS485 NB-2010 as a single-door bidirectional controller, NB-2020 as a two-door bidirectional controller, and NB2040 as a four-door unidirectional controller. 

 The second category supports TCP/IP communication NB2010T for a single-door two-way access controller, NB2020T for a two-door two-way access controller, NB2040T for a four-door one-way access controller.

Third, the prototype of the controller two-door and single door support two-way, why the four-door controller only supports one-way? Is it possible to connect two card readers in parallel with one card reader connector?  

 The four-door card reader of Nabon only supports one-way, due to cost and actual customer needs. Because we have calculated the needs of customers, if a customer wants to go on dozens of doors, generally only a few of them need to read the card two-way, most of the doors are still only one-way read the card. If the door together needs to read the card bidirectional, you can choose a double door or a single door controller, if there are four doors together need to enter and exit the card, you can choose two double door bidirectional controllers. 

 Some customers have suggested that it is possible to have a card reader connector and connect two card readers. In theory, it is not possible, two card readers may affect each other and damage the card reader and controller, read the card record can not distinguish is the entry record or the exit record, brush a card may produce two records. Although it is not a big problem to test the connection on the desktop, we still recommend that you do not do so to avoid the trouble of equipment damage in the future.