Tach Reading or Voltage Reading

I've begun the install of my remote starter, and want to know if I should use Tach check or Voltage Check. Also, could someone please explain to me what each of these mean?

-use tach whenever possible. (reference to DEI units.) -if engine checkin ON, the RS will monitor the tach(engine RPM) or voltage (whichever mode you use). ----if it see tach's RPM is too high, it shuts off. TACH mode doesnt concern w/ crank time. ----if it see voltage is dropping drastically (like if youre to jump start another car or turn up ur stereo sys), then it will shut off. VOLTAGE does concern w/ crank time. _______________________________ if youre to turn off ENGINE check mode, then it will not monitor tach nor voltage.Houston,TX

"The two most common elements in the universe are H+ and stupidity" (Ellison).

Awesome...you really helped me out there :) Thank you