need operating help with racal dana 1992 counter

Hi,

I am testing out one of these units and I am puzzled by its response.

1. If I put the same signal into a and b and set the function to ratio a/b I expect to see 1. Instead I see 0.

1. Same as 1 but with using input c instead of a and ratio c/b.

2. I note that the trigger led on input b is lit constantly. This does not seem right.

If you have experience with this counter, please respond.

Many thanks