Control Unit IV Reference Manual Troubleshooting
529-0004 Ver.3 6-7
6.3.2 Modems
If you are unable to establish a modem link between the Control Unit and a computer, use
this procedure to check the settings for the connection. Note that when you use an external
modem, the Control Unit’s modem LED is off.
1. Make sure you are using a null modem cable to connect the Control Unit and the modem
(see Appendix B for more information on cables). The modem must be connected to
COM 1 or COM 2. Check the cables, the telephone wire, and the power. Refer to the
modem manufacturer’s documentation to test your modem.
2. If your modem is working, check the communication port settings on the Control Unit
and on the modem. The Control Unit’s communication port setup (COM 1 or COM 2)
must be the same as the modem’s setup (contact Electroline for details on modem setup).
Specifically, check the following:
• The transmission speed should be the same on all connections, i.e. between the
Control Unit and its modem, between the two modems and between the other modem
and the host computer.
• Make sure that the flow control conditions have been met. Usually, hardware flow
control (CTS/RTS) is used on these connections, on the condition that all the devices
have been set up with hardware flow control. If no flow control is used, then you
must insert a line delay of 100 ms or set the connection speed to 1200 bps. For more
information on configuring modems, contact Electroline’s technical support
department.
• Make sure that the right protocol and flavor (type) of protocol is installed (see
Chapter 3) so that the host computer and the Control Unit are able to communicate.
Note that the ICOR protocol uses the Control Unit’s ID code. If you are using the
ICOR protocol, you must make sure that this code is valid, or change the ID code
(see Chapter 3).
3. If the ports are set up properly, make sure that the host computer’s port is not being used
by another application or device. If necessary, reboot Windows to free up the PC’s ports.
4. If you are still unable to establish a connection, reset the Control Unit by triggering the
reset button. In a redundancy system, turn off the units and then turn them back on (see
section 6.4.3 on page 6-10 for instructions). If the problem persists, contact Electroline’s
technical support department.
6.3.3 Terminals
If you are unable to communicate with a terminal that is connected to one of the Control
Unit’s ports, use this procedure to check the settings.
1. Refer to section 6.3.1 for instructions on checking the COM port setup. Make sure that
the Terminal protocol is installed (see Chapter 3).
2. If the port is set up properly, make sure that the host computer’s port is not being used by
another application or device. If necessary, reboot Windows to free up the PC’s ports.
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