Need technical information about FXS ports on ATA-186 and VG224

Unanswered Question
Nov 16th, 2007

I need information about: how many telephones can be connected in parallel,in one FXS port.

I have this problem too.
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Paolo Bevilacqua Fri, 11/16/2007 - 04:55

ATA - 5 REN. VG i think the same, it's in the tech specs.

Hope this helps, please rate post if it does!

rob.huffman Fri, 11/16/2007 - 07:04

Hi SD,

Just to add a note to the good info from Paolo (nice work!). The actual number of devices will depend on the REN (see below) of each phone plus the distance away from the ATA or VG224. Any Analog phone should have a REN # in their specs.

Ringer equivalence number

In telecommunication, a ringer equivalency number (REN) is a somewhat arbitrary number which denotes the loading a telephone ringer has on the line.

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 desk telephone. Note that modern telephone equipment may have a REN significantly lower than 1: as a rough guide, externally-powered digital-ring phones may have a REN as low as 0.2, while modern analog-ring phones (where the ringer is powered from the phone line) typically have a REN around 0.8.

The total REN for a subscriber's line is simply the sum of the RENs of all devices connected to the line; this number expresses the overall loading effect of the subscriber's equipment on the central office ringing current generator. The local telephone company usually sets a limit on the total REN, typically 5 or less.

If the total allowable REN load is exceeded, the phone circuit may fail to ring (or otherwise malfunction). In extreme cases, the telephone service provider may temporarily disconnect an overloaded line to reduce load.

While REN is a United States-developed yardstick, analogous systems exist internationally. In some countries, (particularly in Commonwealth nations), the REN is better known as the ringer approximated loading number (RAL). In the United Kingdom it is called the ringer equivalence number and a maximum of 4 is allowed on any British Telecom (BT) line.

From Wikipedia;

http://en.wikipedia.org/wiki/Ringer_equivalence_number

Here is the ATA information;

5 REN 200 feet (61 m)

4 REN 1000 feet (305 m)

3 REN 1700 feet (518 m)

2 REN 2500 feet (762 m)

1 REN 3200 feet (975 m)

From this good doc;

http://www.cisco.com/en/US/products/hw/gatecont/ps514/products_administration_guide_chapter09186a00800c4d1c.html#1034692

So, if your phones have a REN of 1.0 and you were less than 200 feet from the FXS you should be able to connect 5 phones in parallel :)

Hope this helps!

Rob

etmarcof Tue, 07/15/2008 - 15:17

Hi,

This is also true for VG224 connected with phones in parallel?

Anyone with one deployment like this working?

Regards,

MC

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