There are two types of Scitsu.....................one is hard wired into the
loom and gets it's 12v supply from the bike battery
the other has it's own internal battery and needs to be charged from a 12v source using a charging lead that comes with it.
The one with it's own battery has a single black wire leading from it and a small jack plug scocket where the charging lead goes. The single black wire needs to be cable tied along the length of the HT lead on two cylinders from different coils...............that last bit is from memory. I'm sure there is a website for the guy that makes/sells/services them.
Just found it but not explored it
http://www.scitsu.co.uk/docs/main.htm
TBH I found the rechargeable one a real pain in the ar5e..................eventually it wouldn't hold a charge...........I paid to have it serviced but it only lasted one more season in the end I got a hard wired one................BTW I'm talking about having it one my old CBR600 steely.............still got it.
I'm very happy with the rev counter supplied by Mr Kawasaki