User's Manual

Elpro Technologies 450U-E Wireless Ethernet Modem & Device Server User Manual
36 www.cooperbussmann.com/wirelessresources Rev Version 1.4.0
Local Register (501) specifies a general purpose Bit Storage area in the local module (Unit B).

I/O Count (8) specifies that it is passing 8 I/O points. 
Function Code 02: Read Discretes specifies the standard Modbus function code to read a digital input. 
Destination Register (501) specifies the register location on the remote Modbus RTU Slave (Unit A). 
Device ID ( 5) is the Device ID of the Modbus RTU Slave at Unit A. 
Comms Fail Register ( 509) is the local Register location that will indicate a communication failure for this 
mapping.
Care should be taken to ensure that the Device ID (i.e. Modbus Address) of the remote serial device
is different to the Device ID of the onboard Modbus TCP Server (if its enabled, the TCP Server only
needs to be enabled if the I/O registers are to be read from another external TCP Client).
Repeaters (WDS) 3.9
Wireless networks can be extended by allowing Access Points to behave as repeaters and forward traffic to other Access
Points. Access Point to Access Point communications is also known as WDS (Wireless Distribution System). The 450U-E
offers very powerful WDS configuration, allowing mesh network technology with self-healing functionality. Alternatively,
fixed AP to AP links can be configured for optimized throughput.
Each 450U-E Access Point supports up to 3 Virtual Access Point or 5 virtual Station/Client connections to other devices.
The WDS virtual interfaces will always be bridged with the main wireless interface
A WDS bridge interface allows traffic to be bridged to another Access Point on the same IP network. WDS bridge
interfaces do not require additional IP Address configuration, as they are bridged with the standard wireless interface that
is used for connections to associated clients. All of the WDS interfaces on the one Access Point may be bridged if
required.
WDS bridge interfaces have the advantage that redundant paths are permitted when using the bridge Spanning Tree
Protocol (see section 0.0 Bridge STP (Spanning Tree Protocol) ), thus behaving as a self-healing mesh network. Bridged
networks are also not as configuration intensive as routed networks. Since WDS bridge interfaces generally do not require
IP address configuration (they inherit the IP address of the standard wireless interface).
Figure 39 - WDS Repeaters