Distance Limitation

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Jan 4th, 2009
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What is the distance limitation of a Cisco IP phone - 100meters? If so what cost-effective products are available to boost this distance to say 1,000meters? Also what is the distance limitation from an analog gateway (V224) to an end-unit analog device?


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Overall Rating: 5 (3 ratings)
Mark Yeates Sun, 01/04/2009 - 14:59
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I can answer the first part of your question. The limitation you are thinking of are the maximum distance of UTP cat5/6 which is 100 meters. You could use a set of media converters to extend the distance between your switch and IP phone. You will need to run fiber optic cable to be able to extend your LAN that far. A set of media converters run a few hundred dollars for a pair.



Rob Huffman Sun, 01/04/2009 - 16:10
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Hey Jon,

Just to add a note to the good tips from Mark (+5 points Mark).We use the VG248 (the VG224 older brother) to supply an Analog device at one of our Grounds Buildings which is at least 600m away. This is via a Tie Cable (24 gauge wire). The max distance listed by Cisco is 975m for a phone with 1 REN. The specs are for the ATA, but the VG's should be quite comparable. Have a look;

This info is from an old Cisco doc;

Q. What is the maximum distance from which I can drive an analog device with a Cisco ATA?

A. Table below provides maximum distances for this question.

Ring Loads and Distances

Ring Load (per RJ-11 FXS Port) Maximum Distance

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)

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;


Hope this helps!


Rob Huffman Mon, 01/05/2009 - 05:53
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Hey Jon,

You are most welcome! Martin, +5 points for this excellent info.

Cheers Guys!



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