RS232 CONNECTIONS
Check your cable against the following diagrams. RS232 is limited to communicating at distances of < 50 Ft. For testing purposes connect a short cable directly from the computer to the machine.
TESTING
The RS232 breakout box is connected inline with the cable to monitor the communications signals. It has about 10 tristate LED's which monitor the signal lines indicating one color for positive voltage, another for negative and off for 0V.

Emotiva xmc 1 firmware update instructions for mac. The following chart indicates the LED states for the listed conditions. The box is plugged is inserted on the control side of the cable.

S1S2S3
SDTogglingNegNeg
RDNegTogglingNeg
RS, CSPosPosNeg
DR, CD, ERPosPosNeg
S1Control Downloading Properly
S2Control Uploading Properly
S3Power up state or after DR OFF alarm occurred

If any of the signals are 0V or at the incorrect level this indicates a problem with the device controlling that signal. When the breakout box is inserted between the cable and the CNC then SD, RS, CS, DR, CD, ER are controlled by the CNC and RD is controlled by the computer. If it was inserted between the computer and the cable then the exact opposite is true.

Fanuc Handy File Manual

Fanuc Manual Guide I Simulator

If you are using a meter then the Positive level is 8.5 Volts and the Negative level is -8.5 Volts from the control. Your computer should be emitting similar voltages.

NOTE:
On all Fanuc controls, pin 25 of the RS-232 port is supplied with +24v from the control for use with specific GE Fanuc devices (ex. Handy File). DO NOT connect this pin through to your PC or it may be damaged