What kind of VSS signal is the E39A looking for?

I have an old school transmission hooked to an LHU and can't get a speed reading. I have a Dakota Digital adapter that hooks into a speedometer cable drive on the trans and it sends a 128K pulses per mile signal. The LHU didn't recognize that so I got a Dakota Digital Universal Speedometer Signal Interface that is supposed to convert nearly any input signal to nearly any other output signal. I have tried different things but nothing has worked. I have tried many different settings in HPT including setting it to manual transmission and the various automatic transmission. Either I get a constant speed readout of 158 mph or I get a constant 0 mph readout. If I know exactly what signal the E39A is looking for, I can get the Dakota Digital tech guys to tell me how to get that signal out of their box.