Reading RSL frequency accurately depends on the meter that you use. Healthy RSL frequency toggles between 1226 and 1234hz AC.
Fluke 87V auto ranges correctly and will give you an accurate reading immediately.
Fluke 177 or 179 does not. These meters require manually ranging to 600mv AC and then selecting the frequency function.
I have seen problems at 1220hz and at 1250hz. 1226-1234 is fairly critical.
