How do you wire Vtec?

Ok as many of you do or dont know im in the process of a d16z6 swap in my 90 crx dx. Im running a rpm activated switch to activate vtec. Now how do I wire in vtec? Some one told me that all there is, is 3 wires Positive, Negative and a wire from the rpm switch to activate the vtec selinoid. Is this true? Or do i need some wires from a 92-95 harness. Please help

If your running obd0 then all you is the switch and a relay, if your running obd1 get the si cpu.