Perle Systems Application Note
Most access control systems for personnel access utilize a serial connection between the access control computer and the card reader/clock. This restricts the distance between these to be no more than 20 meters and may require the use of multiple access control computers. By connecting the card readers over an Ethernet network using a serial device server, a single computer can now read and control each reader, resulting in a more secure system and reduced costs through increased efficiencies in employee database management.
Device Servers with Integrated I/O Control
In addition, a device server with digital IO can extend the security of the system by providing centralized control from the access control computer to open doors, open gates or sound alarms.