Author Topic: REN - Ringer Equivalency Numbers (continued: The fine point bickering discussion of REN)  (Read 740 times)


  • Guest
Sometimes the truth needs to be said.  Common sense doesn't prevail.

I made an innocent remark that REN isn't accurate, and that a nominal voltage of 40v leaving a carrier grade Alcatel-Lucent Optical Network Terminal couldn't handle a ten button payphone from 1967 (Northern Electric of course).

I was perplexed.  REN was never an issue on the Digital Multiplex System.

The best way to explain it to anyone is the plumbing analogy.  Our Venture DTAD phones were 1.4 REN A (or 30 LN), which meant you really couldn't have more than three on a line, although the system could handle 8.  And, they rang off a transformer connected to an electrical outlet.  Explain that one.

I never spoke to the engineers as to why that was the case.  The ringers were electronic.  The whole project was hush hush as it was the first key-less system in the world.  I have my suspicions.

An old phone once rated at 1 REN is not 1 REN.  It's more, because the magnets are old.

Venture DTADs are $500 a pop, so one guy but sandman's ring booster, and he fried two DTADs  -- $1000 down the drain.

Plus, is it a square wave, trapezoidal.

Victor, be a man, and don't go cry to mommy moderator.  Debate is healthy.

That is so cliché ... "ad hominem" -- you're clearly one of the profs I had in university in digital electronics.

Put the information out -- let others decide.  If Ericcson/Telecordia/Bellcore/Whatever changed the rules after the fact, it doesn't mean they were retroactive and applied to phones built 30 years prior.

On long loops, we used a different gauge of wire, just so you know.  REN and LN was a system to dumb it down.  Nobody in the industry went by them.  You need a special meter to separate the DC and AC measurements.

Electronic ringers are very forgiving -- electromechanical, not so much.
« Last Edit: July 03, 2017, 11:55:04 AM by a moderator »


  • Guest
DSK ... please remember the standard here was 90v sinusoidal RMS AC superimposed over the DC signal.  In Europe, it was 60ish at 25 Hz.  I have the worldwide table.

If we put in in loop reversal on answer, the line's polarity would reverse, and then ring with reverse polarity, and upon answer, we reversed the polarity back to normal.  Some ringers choked.

Fluke meters can separate AC and DC, but they're still not 100% accurate.  Stay away from ring boosters.  I have an entire book on ring generation in DMS.  If anyone wants to see it, I'll post it.  It really is something to marvel at.

Even pulse dialing -- the digital analytics were so friendly, dial calibration was unheard of.  Nothing was fixed -- it was all relative.

For 302 phones, I usually recommend the Meridian Option 11 analog line cards, with one 302 on each.  They emulate 1A2 or residential, but are hard to find.  These were the ones with voltage message waiting indication that went quite high (over 100v DC) -- which of course didn't set off the ringers.

They became obsolete with CLASS FSK MWI and digital sets that simply said "ring"