> Do you know how much current you need to source on the 48v
> signal, i.e.the load impedance of the dyno?

It's fairly high. I don't have the schematic here but recall that the DC
input was split and buffered by transistors. There was also a meter
with 22k in series. I thought at the time 100mA would probably do it

I did say it's an old machine, not a modern bells-and-whistles digital
monster with s/w and displays. It's calibrated in mph (archaic for this
country)

> Do you already have a supply voltage available for your interface?

Just 12V
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