Q: What’s the best way of networking access control units?
A: This is dependent on the exact customer requirements and the circumstances at site. To answer this I’ve split the question into three separate parts to address the primary methods of communication used.
1: Dedicated access control networks: The conventional method of installation, dedicated networks most often use the RS485 communication protocol. This offers adequate speed, resilience and distance without requiring specialist installation techniques or expensive cable. Whilst a dedicated network does mean that a cable has to be run around the building to all access points, this isn’t always a big issue. For applications where this is practical the RS485 option offers independence from other building systems and infrastructure. This can have advantages including system resilience, fault finding and it narrows the scope of the installer’s liability. The access control runs on a network that you have installed.
2: TCP/IP: People have been banging on about TCP/IP for years. In theory we should all have pencil sharpeners that are connected to the internet by now. It’s true that in many cases TCP/IP is brilliant and perfectly suited for access control systems, however this isn’t always the case. One great advantage of using TCP/IP to connect your access control units together is that you are using an existing data network which can make the installation quicker and easier. Also the TCP/IP network has security and data resilience built in. It may well be that the network has been configured to be resilient in the event of equipment or power failure, making it a very reliable communication platform. Another great thing about TCP/IP is that, if a Wide Area Network exists, access control systems can be set up over several remote buildings relatively easily. On the negative side, there are some specialist installation and fault finding skills required. Also the relationship between security companies and IT departments is not always harmonious (You’re not sticking that *@#% on my network!).
3: Wireless: Using wireless technology for security systems has been somewhat tainted by the budget intruder alarm products that have been popular through DIY outlets. If, however, the right wireless technology is used and implemented properly, wireless control units have real value as part of a professional access control system. The most important consideration is that the wireless connection should not be relied upon for permitting or denying access to users. This decision making should be handled using distributed intelligence at the control units. Applications such as car park barriers are particularly suitable for wireless control units as there is quite often mains power available but no easy way of cabling for the data connection. Old buildings can also be particularly difficult to cable and so are perfect candidates for wireless control units. Where a TCP/IP network exists, a wireless connection can be used for the difficult last 15m.
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