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REN - Ringer Equivalency Numbers

Started by benhutcherson, October 21, 2008, 07:21:49 PM

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Quote from: JorgeAmely on September 19, 2009, 06:07:40 PM
I wonder what the A and P units are?
Probably the P measurement is Peak, and the A is Average.

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To increase the confusion I come with a new theory.
REN = Ringer Equivalent Number in the bell system this will equal the most common ringer at the time introduced, the ringer in a std. 500 telephone.
Later this has been the base of an international standard. The modern ANSI/TIA-968-B specification (August 2009) defines 1 REN as an impedance of 7000Ω at 20Hz (type A), or 8000Ω from 15Hz to 68Hz (type B).

Before this different countries or telephone companies was making their own standards if the want.

Here i  Norway, the rule was max 2 ringers on a line. When we measure a Norwegian ringer against the 500 telephone the current consumption is nearly 2.5 times the 500, and should be deemed to be 2.5 REN ringers.

Whats the point of this strange unit? REN!
It was used to define the max allowed ringer load at a line still working well. At a short line The current will be higher, and the exchange may see the high load as someone going offhook, On a long line with high voltage drop, it should still be power enough to run a sudden number of ringer motors.

My 1948 PAX indicates off hook when i load it with more than approx 3 REN. (Short lines)
This problem indicating off hook would never happen if I used the British system with master socket and one common capacitor.

What about the suffix? Just guessing: A for ordinary frequency ringers 20Hz (25 in Europe) All other letters indicates non std frequency.


OK, here an easy one...... I have 4 phones in my home, 1 in the bedroom, 1 in the kitchen, 1 in the livingroom and 1 in the front den..... now, why do my phones all fail to ring right when there is a call???? in the bedroom, I have a WE 307C.... in the Kitchen I have a 444E, in the livingroom I also have a 444E... and in the front den I have a 2564.... the phones all start to ring in the first ring, and then just the kitchen extention sounds and the rest are quiet.... any idea why???


Try disconnecting one phone and see if the remaining 3 ring. If the three don't ring, disconnect another and see if the remaining 2 ring. At best, COs provided up to, I think, about 5 REN but with modern phones needing anywhere from .1 for external powered digital phones to .8 for analog phones, your CO may have reduced power to you house. Seems 4 phones, assuming each of your phones is 1 REN, is too big of a load for what is being sent to your house. Your phones may also have 1.25 or some other higher REN which in total overloads the power available on your POTS line.

I'm sure others who know more than I will clean up this thought with better facts.


There are usually other factors to consider, the distance to the telco's hardware, the age of the copper wires to you house, the quality of connections to your house, and the phones themselves which may not be 1REN each, so could be overloading your line...

One option would be a REN booster, giving your line some more juice supplied by your mains power, or the other option, a small phone system like the Panasonic KX-T308 or T616, providing 8 or 16 extensions respectively, along with 3 or 6 incoming lines... :)


The ren load is the easiest thing to test, just try to reduce the number of ringers connected.
If 3 phones rings, you know the answer.
It is several ways to reduce that load. The most common is serial resistors, who just consume energy to heat the resistor, and you get even weaker ringing.  One of the "forgotten" ways:Wire 2 of the telephones for grounded ringing. One for tip to ground, and one for ring to ground, but you do not ground them, just connect the ground wire from the 2 phones together, then you get 2 ringers in series, a little weaker ring, but better than using resistors.

If the 2 ringers in series are different one will ring louder then the other.



Have you also put the bias spring in the low position on each ringer?
"C'est pas une restauration, c'est une rénovation."--François Martin.


How is REN determined?
Does one REN=X milliamperes?


Different telcos has different standards. The most used definition is from Wikipedia:

A ringer equivalency number of 1 represents the loading effect of a single "traditional" telephone ringing circuit, such as that within the Western Electric Model 500 telephone. Note that the REN of modern telephone equipment may be significantly lower than 1: as a rough guide, externally-powered digital-ring phones may have a REN as low as 0.1, while modern analog-ring phones (where the ringer is powered from the phone line) typically have a REN around 0.8.

In the United States 1 REN was formerly equivalent to a 6930Ω resistor in series with an 8 µF (microfarad) capacitor. The modern ANSI/TIA-968-B specification (August 2009) defines 1 REN as an impedance of 7000Ω at 20Hz (type A), or 8000Ω from 15Hz to 68Hz (type B).

The measurement in milliamps will not be linear, but; when I measure the load at my P.O.T.S. line I get a voltage of approx 95V with no load, and a mA reading of approx 10 mA per REN in the range from 1-4 REN. 11-12 mA at one REN and 39-40 at 4 REN.

This reading will depend on the line and exchange resistance and impedance. The wire length to the exchange are approx 7-8 hundred meters.  


Some new measures here:


I have done some measuring at my POTS line, and tested 2 well known phones.
My conclusion will not be any scientific break trough  :) just again confirming the impossibilities of masuring REN no at the line.

The picture tells about the result, my conclusion is again, we cant measure this because of the line complexity. The length and the exchange equipment will make problems for this measurement. The only way to tell how much load your line has capacity of is to increase loud until you get problems, and then reduce to its working well.

A hint will be if the ringing current exceeds twenty-something mA, or the ringing voltage drops considerably under 60V you may expect problems, whatever happens first.





Complex or not  ??? At lest its no easy way to know what I may put on my line, and whats happening before i just test it. I have a wide range of telephones, from the typical German 600 ohms +1 uF ringer to modern ones. Changing one telephone with another may result in different results. To high load may result in false off hook detection, to big difference in the ringers, may cause one to be weak, but others still rings with a loud ring.  My simple REN no calculation of the Standard telephone is simply done by ringing a 1 REN ringer at 25Hz at 70V and measuring the current (2500 telephone), measuring the current on the unknown ringer and determine the factor.

The old Norwegian rule was a max of 2 telephones on one line, by my simple calculations/measurement the typical ringer was about 2.5 REN (This has never been used terminology here). Usually it was no problem adding the 3'rd ringer, but don't tell anyone, and of course you payed extra for renting all extra equipment. The extra ringer, often put outdoors did usually not have a bias spring, so you would always know if someone was dialing.



Not to hijack, but has anyone measured what the REN of a 302 is?

Asie: how does one search this forum for complete words only (i.e. so that the search for 302 REN doesn't return posts that happen to contain words that have the three letters "ren" in them somewhere....)?


I have got some help from Ralph O Meyer, The writer of "Old-Time Telephones!"

I really hope I understood his hints, at least I have designed this circuit:

Based on this I did some measuring and ended up with some values.
The values are based on measuring one single phone of each kind, and if we include some inaccuracy, the values should just be indicator within a range of about +/- 10% (I hope)
Since my ringer supply was 25Hz, the 1 REN impedance had to be 8000 ohms.

One of my conclusions are: The ringer resistance does not tell my anything about the REN.
Another may be to add another capacitor in series, or change to a smaller capacitor to reduce the load without loosing to much of the power.



Still my readings gives some strange results.

I'm definitely not sure whats happening when changing capacitor, and greater capacitor gives lower load, and vise versa.