How to hook tach sensor wire?

I am not really know how to hook up the tach sensor wire for remote starter.

I read many remote starter's manual. There are 2 ways for detecting the tach as below.

For example, PONTIAC TRANSPORT 1990-1993

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WAY 1:

WAY2:

R U using the WRAP around Plug or coil method or can U use a direct TACH connection?

I work for a company selling a lot of alarms. So there are many ways to detect the engine starting. But whatever, just give above 4V to that wire on alarm when engine is starting, it will work well. But just not really know which way is the best. For some vehicles, round 5 loops is not working though the manual says it does.

Some alarm's manual says it should connect to engine oil pressure sensor. But it is hard to locate the engine oil pressure sensor wire. Most vehicle's installation wiring sheet only provides the "TACH SENSOR" wire. For this case, mostly, I connect it directly to the tach wire, it works well. Isn't high volt? But the alarm didn't burn. Why? But if I round 10 loops on the tach wire, it wouldn't work. Why?