Short these conductors at the far end of the cable and watch the meter for continuity readings. Disconnect the cable at both ends and connect an ohmmeter to the ground, and Rx pins. The Ground conductor can only be tested using a meter.

This test will verify the continuity of the Tx and Rx wires in the cable, but does not completely test the cable. If it continues, it indicates there is a short between Tx and Rx in the cable. If you do, remove the short and test again. Again, you should see both Tx and Rx LEDs. This is usually pins 2 and 3, but verify with the cable specs to be sure. Short the Tx and Rx pins together on the equipment end of the cable. If you get lights on both LEDs, move on to the next step.Ĭonnect the cable that is going to the controlled device to the port, and disconnect it at the far end. If only the Tx LED is lighting, the unit is not really sending strings.

You should see both LEDs light when each command is sent. Send a command and watch the Tx and Rx (receive) LEDs. Once you have a good response from the Tx LED, short pins 2 and 3 on the DB-9 or phoenix connector on the port. See later in the document for a discussion of handshaking. Sending an 'HSOFF' command to the device port does this. If your device does not use hardware handshaking be sure handshaking is disabled in the port. If you do not see the Tx LED, you must first correct your code, or configure the hardware properly. You should see the Tx (transmit) LED light. Send a string by pressing a TP button to send a command use Open Axcess, NetLinx Diagnostics or a terminal emulator. First, make sure that your code and/or hardware are sending strings.

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