External Auto Mode in the RC7 allows an external device (such as a PLC through System I/O) to start and stop programs, and issue other System I/O commands. 

Video Tutorial

Step-by-Step Guide

Step 1

Press [F4: I/O]

Step 2: 

Press [F6: AUX]

Step 3: 

Press Int/Ext

Step 4: 

Select External Automatic Mode

Step 5: 

Press OK.

Step 6: 

Press Cancel until you return to the main Teach Pendant Screen.