Telco Ringer Equivilence

Lenp · Post by **Lenp** » Thu Dec 27, 2007 6:23 pm

Greetings All

Here's the issue. We do consulting for s major school district and the the local telco guys often lift the POTS pair on telephone dialers for their security systems.

These dialers do not report failures like modern dialers. They are old, and dumb. (the dialers that is) The reason the telco pulls the pair is because the dialer has a REN of 0.0, so the lines look clean.

Tagging and flagging the lines has not worked so what I am suggesting is to give these lines a REN of something more than 0.0, artificially. This way the lines look like a set is attached and will be less likely to be disconnected by accident.

Sure, we could hang a ringer on the line at the dialer but I think a coil-cap combination would be neater.

Any suggestions...

Len

dyarker · Post by **dyarker** » Thu Dec 27, 2007 7:17 pm

Don't know why they'd lift the pairs (as long as the bill is paid of course)???

They lift it at central office, or at your building entrance?

A cap, coil and resistor in series would work. Cap and coil should resonate at 20Hz (20Hz to 40Hz okay). Resistor to limit AC current during ringing to 5mA - 10mA, maybe 3.3K. That should give a REN of 0.1 to 0.25. I'd have to search the manuals for exact values because this isn't something I worry about on the PBXs I take care of (I know what each line is used for).

C U L,

Externet · Post by **Externet** » Thu Dec 27, 2007 7:21 pm

Hi Lenp
Connect a 1uF / 250VAC capacitor in series to a 8K Ohm resistor across the telco pair.
That will give you 0.5 REN.

L1-----------||----------/\/\/\/-----------L2

Those capacitors are easy to find inside defunct PC switching power supplies.

Miguel

David Bridgen · Post by **David Bridgen** » Thu Dec 27, 2007 7:22 pm

Doesn't have to be resonant, it just has to draw the nominal ringer current so a simpler solution would be just the R and C.

Whoops, sorry Miguel, I was writing my answer as you were posting yours.

Externet · Post by **Externet** » Thu Dec 27, 2007 7:29 pm

Hi David. Just joining ? Doesn't sound right ... Â¿?
Yes, agree, While Dale was posting I was also typing and calculating and trying to find how to enter the Ohms and micro symbols in Linux, till I gave up. I will find them later.
Welcome !

David Bridgen · Post by **David Bridgen** » Thu Dec 27, 2007 7:41 pm

Externet wrote:Hi David. Just joining ? Doesn't sound right ... Â¿?

Just joining this forum, yes.

I was very active on quite a few of the other foums until three, maybe four, years ago when I lost interest. (I think I may have used a pseudonym.) I remember you as a frequent contributor too.

Just testing the water again.

dyarker · Post by **dyarker** » Thu Dec 27, 2007 8:24 pm

True, doesn't have to resonate. But since it will probably just be connected across the line, and switched out by a hook switch, I was trying to keep impedance above 300Hz high.

Test with just a cap and resistor. If it doesn't interfere with the dialer set up, then you've saved the cost of a coil.

Cheers,

Robert Reed · Post by **Robert Reed** » Thu Dec 27, 2007 9:07 pm

Nice web site David and welcome to the forum.

David Bridgen · Post by **David Bridgen** » Fri Dec 28, 2007 6:45 pm

Robert Reed wrote:Nice web site David and welcome to the forum.

Thank you Robert.

Lenp · Post by **Lenp** » Sat Dec 29, 2007 3:50 am

Thanks to all,
I have found that the device is called a half ringer in telephone terms since it has a REN of 0.5. Most versions use back to back zeners along with a .47uf and an 8K resistor across the line. I think DSL has trouble with this, but these are all POTS lines.

Sadly, these telephone systems have been so heavily changed, from an older 1A2 to an Eagle to whoever is the low-baller this week that the wire closets and frames are a nightmare. Nothing marked, tagged or even neatly installed. We refer to it as a frizz- frame since there are so many wire ends sticking out from the blocks.

The dialer lines are often spares that they can find in any cable. I actually found one pair that was turned back on another pair then back again, all in the same cable. When there is a move, or a problem, telco-Joe is called and the fun begins. I find red caps and tags on the floor and inside the cans all the time, so marking doesn't help either.

I didn't create this mess, just trying to shovel some of it up.

Thanks again,

Len

Robert Reed · Post by **Robert Reed** » Sat Dec 29, 2007 2:08 pm

Antone
I been following this post with some interest and one term I've never heard of - that being REN. I am assuming it probably relates to Ringer Equivelnt Resistance. Right? Wrong? Please Explain. Also what do the numbers ( 0.5, 1.0, etc) refer to?
thank You.

Externet · Post by **Externet** » Sat Dec 29, 2007 2:45 pm

Hello Robert.
REN means 'ringer equivalence number' You may see it on the label of a telephone.
The Telco puts out a finite amount of power available with the (US) 20Hz ~90 VAC ring signal, Depending on the Telco can be 5 REN, 1 REN, whatever they want.

The old electromechanical bells used more power -Perhaps 1.0 REN- than the modern optoisolated piezoelectric ringers (~.1 REN)

When several telephones with electromechanical bells were in parallel in a home, it could happen the bells did not chime or faintly did, as they demand more power than the Telco puts on the line.
Removing some of the telephones restored the bells to work again. That was matching the power (impedance) availability of -perhaps 3 REN_

From calculations I did a long a go, 1 REN = 1 Watt if I remember well. This I have not seen ever in any book, and asking telephone technicians you find at a corner armoire fixing things, they have no remote clue.
Same, I calculated 1 REN load to be 8Kâ„¦,---> 2 REN load to be 4Kâ„¦, 0.25 REN load to be 32Kâ„¦, etc
If the Telco puts out 2 REN, you can have up to 4 x 0.5 REN bells in parallel, or 10 x 0.2 REN piezoringers in parallel.

Hope it makes sense,

Miguel

frhrwa · Post by **frhrwa** » Sat Dec 29, 2007 3:20 pm

wouldn't it be easier and cheaper to just put a little electronic ringer on the line pair.. find one with an REN of about .5 or so.. I've seen plenty.. still don't understand the telco lifting the pairs.. it should be in their facility records as a hot pair, and they shouldn't be fooling with it.. if its in the CO for sure its in records, if its at the plant side, or facility side then it should also be in records.. I used to have a lot of problems with some of these "so called" telephone men that would steal a pair if they heard nothing on it.. unfortunately, ground start lines have nothing until you start them.. and they constantly cut my PBX lines off to grab a "vacant" pair they thought...

Robert Reed · Post by **Robert Reed** » Sat Dec 29, 2007 4:27 pm

Exter
Read you Loud and Clear. Thank You.

As far as' making sense', some of the TELCO terminology never will as it seems to be carried over from some ancient age

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Telco Ringer Equivilence

Telco Ringer Equivilence

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