I'm trying to figure out how to measure the REN value of phones(B format). I need to verify the phones that I am using in a test network and want to accurately measure the REN of the phone instead of relying on what is stamped on the bottom. Anybody know a test set that will measure the REN?

Steve

REN is equal to one of the old style Bell System ringers. I don't know the actual measurement, don't know as I've ever even run across the need to. Manufactures have to post it on equipment so it doesn't damage the network, at least that was the original intent. You might try www.sandman.com for a better explanation.

Bill

Don't know why you wouldn't want to rely on the number marked on the set. I suppose if you wanted to see how much they differ from the actual...

The only way you are going to find the official procedure for determining the REN is to do some research on the FCC website. There is a test procedure that telephone manufacturers must submit to but you may have to shell out some bucks for the documentation.

-Hal

Search google for ringer equivalency number there is a lot of stuff. I'm with Hal, why would you not trust the posted REN on a piece of equipment?

>> why would you not trust the posted REN on a piece of equipment?

There could be Government conspiracy lurking! Ooops, wrong forum....

I'm testing a piece of equipment that has incorporated a REN test as a feature. I need to verify that we are correct in our assesment of the phone.

BTW, the old style bell ringers are a REN type of "A". I'm interested in measuring "B".
I basically need a "second opinion" test set to compare against my "REN tester". I've already built a 5 REN test board made from resistors and caps and I know we are off a bit on that.

I think one of the links I googled had the resistance towards the bottom of the page.

As I was taught in phone school 21 years ago, 1 Ren is the amount of current needed to ring a Western Electric single line telephone with a mechanical bell. The phone company was required to provide 5 Ren on a line.

I would see if you can call repair and get through to a test board operator who would probably know someone there who would know.

I've not heard of a B Ren. Someone working in the switch office of a LEC or CLEC should be glad to help you.

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

It's never as easy as you hope. Summed up, I'll need to generate a DC and a AC signal. A few measurements would need to be performed. Hal you're correct, it's in part 68. Here's a quote for those interested. Thanks for your help guys.

In order to determine the REN, for North America, four different calculations are used:
• 25MΩ divided by the minimum measured on-hook DC resistance for an applied voltage of up to 100 volts.
• 150KΩ divided by the minimum measured on-hook DC resistance for applied voltage of up to 200 volts.
• 0.6mA divided into the maximum DC current drawn during the AC on-hook impedance test.
• 8KΩ divided by the minimum AC impedance measured while performing the AC on-hook impedance test (for "B" type ringer).
The largest of these four numbers is listed on the label as the REN of the device. If the AC impedance yields the highest REN (as it usually
does), it is followed by a letter corresponding to the type of ring signal applied during testing. For example, if the highest REN calculated was
0.8, and the device was tested as a B type ringer, the REN would be 0.8B.

I knew that. :rolleyes: I'll bet it's more of a guess than a test now days. I'm sure there is a test set out there somewhere you can just hook a piece of equipment to that will give you the REN value. Thanks for the info.
Bill