I'm testing a piece of equipment that has incorporated a REN test as a feature... I'm interested in measuring "B"

Like I said, get it straight from the horses mouth. The test procedure that is used to determine REN is dictated by the FCC (part 68 I believe) acceptance testing. It's been many years since I was involved with that end but if you want your test to have any validity you are going to have to use the same procedure that every manufacturer had to submit their equipment to originally. As I remember the FCC documentation did detail the difference between "A" and "B".

It's probably very simplistic to believe that you can simply measure resistance or impedance or compare 1 REN to the current drawn by a Western Electric ringer. That's what it's supposed to be but a lot has changed over the years.

Understand first how it's "offically" determined then base your procedure on that. Any other way is a shot in the dark.

-Hal

CALIFORNIA PROPOSITION 65 WARNING: Some comments made by me are known to the State of California to cause irreversible brain damage and serious mental disorders leading to confinement.