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8 - PC400 Terminal Installation & User’s Guide
RS-485 Connections
An RS-485 connection can attach up to 31 clocks to the computer, using a SWIFT-485+
converter that you can purchase from Lathem. You can wire the clocks directly to the
converter (star configuration) or wire them to RS485 Terminal Screws; this allows you to
run in a single line starting from the converter (multi-drop configuration).
With an RS-485 connection, you can use up to 4000 feet of cable to connect your clocks
to the computer. Lathem recommends using CAT 5-UTP (unshielded twisted pair) data
transmission cable.
To make an RS485 connection
♦ Connect a SWIFT-485+ converter to an open COM port on your computer. If your
COM port has 25 pins, you will need a 9-to-25 pin adapter that you can buy from a
computer store.
♦ Run the CAT 5 cable from the Swift-485+ to the first clock in the series .
See Appendix A for the RS485 Network diagram
♦ Unplug the RS485 screw terminal connector and attach a matched pair from your
cable as shown in the diagram, plug in the connector. Make sure that the polarity is
maintained. If your cable is terminated with a RJ-45 plug connect to the Terminal’s
RS232 / RS485 communications port as shown in the diagram below, Figure 4.
RS232/RS485
Port
RS485 Screw
Terminal Connector
(-)
(+)
Figure 4