Apex V-AFC VTM Wire? What is VTM

Hey i was looking at the install on the APEXi V-AFC and it talks about the VTM wire.. what exactly is it.. and does the p13's have them? Im just curious because it says some models do not have them.

 

I stand corrected it says VTM signal.

 

Hook it up. I never found out what it was either, even from Apex, but I was throwing a CEL, and vtec was cut out at a certian point, once I hooked it up, all was right.