Specifications

October 8, 2003 Networking Alpha Signs (9700-0112C)
50 Appendix
Appendix B—End-of-line termination
When an Alpha sign is at the end of an RS485 network, a special end-of-line (EOL) terminator is required for
the first and last sign. The EOL terminator plugs into the sign’s RS232/RS485 port and stops the flow of
communication.
On an RS485 network, the PC that sends messages to the networked signs is wired directly to one of the signs
using a Converter Box III, which converts the computer’s RS232 signals to RS485 signals. In this case, the Converter
Box III must be terminated instead of the first sign in the network. To terminate a Converter Box III, set the switch
on the back of the unit to Terminated:
Sometimes, the PC that sends messages to the networked signs is not directly connected to any of the signs.
Instead, the PC sends messages to a modem or wireless transceiver attached to the signs. The messages are then
relayed to the other signs in the network):
First sign
Last sign
Middle sign(s)
Converter Box III
(pn 1088-1111)
RS485 Termination ON
End-of-line (EOL)
terminal or required
RS232
RS485
End-of-line (EOL)
terminator required on this
sign if it is the only sign.
RS485 Termination OFF
RS485 Termination OFF
RS485 Termination ON
RS232
Wireless transceiver
First sign
Last sign
Middle sign(s)
End-of-line (EOL)
terminator required on this
sign if it is the only sign.
RS485
Modem
Termination by
dipswitch required.
RS485 Termination ON
RS485 Termination OFF
RS485 Termination ON