The Classic Machinery Network

Hi all,
I have been looking through the site for an answer but can't quite find it... Would anyone out there know where the electronic tacho is connected? I think it is the alternator, but I'm not just sure where and I Don't really want to fry the days by connecting it to the wrong place. The alternator was changed by the previous owner and replaced by a Lucas equivalent (prestolite)..
Is this a common thing?
Thanks.

It should be connected to the alternator.The alternator needs a 'W' terminal though. If there is no W terminal on the replacement alt,a good autospark should be able to fit one to it but a correct alternator could be the better option.