When a client asks, “Can we use our existing keypads on another access control system?” I most likely have to tell them no, unless the system uses a standard communication protocol. I recommend using an industry standard such as robust Wiegand format keypads and card readers.
Wiegand is the most common method of communication used by access control devices, and it’s used worldwide by security and access control manufacturers. RS485 keypads and card readers is a proprietary communication protocol designed by each manufacturer to communicate specifically with their systems.
Not only are the keypad and card reader communication protocols important, you also need to look at the way they are being controlled by different controllers.
PC-based controllers utilize the host PC to perform all the access control decision-making, and have no master controllers. These system types rely solely on the PC to operate the keypads and card readers. If your PC is turned off or if the program isn’t running, you have lost your security system. Most of these systems use a proprietary keypad format and are not interchangeable with other access control systems.
Single-master control units have software on the PC to receive or upload tenant information and/or activities. These systems do not require that the PC be on to operate. The keypads and card readers are slave, semi-intelligent devices that are controlled by a single RS485 line. These systems also use a proprietary keypad format and are not interchangeable with other access control systems.
One RS485 keypad can affect the communication for the entire RS485 line and stop your system from operating; this can also be very difficult and costly to troubleshoot. On larger systems, the reaction time to open gates or doors slows down even if all the devices are online.
Distributed database, multiple intelligent control panels include single-gate/door controllers as intelligent keypads and card readers, and 2-4 gate/door controllers. These controllers can communicate to the host PC through several options—standard network TCP/IP protocol (wired and wireless), USB, RS232, and RS485.
Unlike the other controller options that use a single master controller, these control panels maintain all the programming including the codes and cards for each tenant. This becomes a very important feature on a larger system if you are having wiring or hardware issues between buildings; each panel serves as a master controller when the communication is lost to the host computer.
Each keypad and card reader is isolated from the others on the controller and plugs into its own port. This is a very robust approach that keeps one failed device, whether it’s hit by a power surge or wiring damage, from affecting the balance of the system and continues to operate your gates and doors.
When upgrading or designing an access control system, a controller that integrates well with other components and includes safeguards against a failed device will make your security system more reliable.