It's a option in tuning software not something you wire in with the standard ecu, you would need a chipped/socketed obd1 ecu. Hondata, Crome, Ectune all have this option "MIL shiftlight" basically you set the desired rpm and the engine check light will flash when you reach this rpm.
if i want to use another type of swift light ?
i will use a different gauge ?
I got a pivot shift light. Connects to cigarette lighter and that's it. Senses the rpm and comes with three lights