It depends what car your going on about doesn't it really? I think in this case your the one not talking much sense mate.

Next time don't ask such a broad question. And say: does my Rev counter attach to the ignition module in my rover metro?

And just so you know the ignition module doesn't 'send' a signal to shit. Your Rev counter may connect to the coil some where to pickup the high voltage flyback or it might connect before the ignitin amp and look at the low voltage signal fed to the amp.