Robert is right, Mat J and I both have these Fox Valley units. They are very nice but they are NOT a standalone unit. That's because you have to type in a 20* offset and use *ATDC which can't be done on a timing light alone. It works beautifully if you have a snap on or Rotunda or Kent Moore with the right pickup...I was thinking it needs to have an inductive pickup to use rather than the magnetic pickup. In truth you probably need both. A snapon timing meter requires two inputs to set the timing right. Could be a luminosity probe and a magnetic pickup, a magnetic pickup and an inductive pickup. it seems many combos are possible, limit is available parts for these obsolete units and using correct offset #s.