Ringer equivalence number
Encyclopedia
In telecommunication
, a ringer equivalence number (REN) is a somewhat arbitrary
number
which denotes the electrical load a telephone
ringer has on the line
. In the U.S.
, this is determined in accordance with ANSI/TIA-968-B (August 2009).
REN is a United States
-developed yardstick
, but analogous systems exist internationally. In some countries, (particularly in Commonwealth
nations), the REN is better known as the ringer approximated loading number (RAL).
, 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).
s 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. For example, Call waiting
and caller ID
are often affected by high REN. 20th century equipment tends to contributes larger REN than new equipment. In extreme cases, the telephone service provider may temporarily disconnect an overloaded line to reduce load.
Some analog telephone adapters for Internet telephony require analog phones with low REN, but researching RENs online is difficult because manufacturers and sellers seldom provide that information. However, the AT&T 210 is a basic phone that reputedly has a REN of 0.4.
it is called the ringer equivalence number and a maximum of 4 is allowed on any British Telecom (BT) line.
In Canada it is called a Load Number (LN); which cannot exceed 100. (The LN of each device represents the percentage of total load allowed).
In Europe 1 REN used to be equivalent to an 1800Ω resistor in series with a 1 µF capacitor. The latest ETSI specification (2003-09) calls for 1 REN to be greater than 16 kΩ at 25 Hz and 50 Hz.
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
, a ringer equivalence number (REN) is a somewhat arbitrary
Arbitrary
Arbitrariness is a term given to choices and actions subject to individual will, judgment or preference, based solely upon an individual's opinion or discretion.Arbitrary decisions are not necessarily the same as random decisions...
number
Number
A number is a mathematical object used to count and measure. In mathematics, the definition of number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers, and complex numbers....
which denotes the electrical load a telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
ringer has on the line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...
. In the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, this is determined in accordance with ANSI/TIA-968-B (August 2009).
REN is a United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
-developed yardstick
Yardstick
A yardstick is a straightedge used to physically measure lengths of up to a yard high. Yardsticks are flat wooden boards with markings at regular intervals.-Construction:...
, but analogous systems exist internationally. In some countries, (particularly in Commonwealth
Commonwealth of Nations
The Commonwealth of Nations, normally referred to as the Commonwealth and formerly known as the British Commonwealth, is an intergovernmental organisation of fifty-four independent member states...
nations), the REN is better known as the ringer approximated loading number (RAL).
Explanation
A ringer equivalency number of 1 represents the loading effect of a single "traditional" telephone ringing circuitElectrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
, such as that within the Western Electric Model 500 telephone
Model 500 telephone
The Western Electric model 500 telephone series was the standard desk-style domestic telephone set issued by the Bell System in North America from late 1949 through the 1984 Bell System divestiture. Millions of model 500-series phones were produced and were present in almost every home in North...
. 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
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
1 REN was formerly equivalent to a 6930Ω resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
in series
Series and parallel circuits
Components of an electrical circuit or electronic circuit can be connected in many different ways. The two simplest of these are called series and parallel and occur very frequently. Components connected in series are connected along a single path, so the same current flows through all of the...
with an 8 µF (microfarad
Farad
The farad is the SI unit of capacitance. The unit is named after the English physicist Michael Faraday.- Definition :A farad is the charge in coulombs which a capacitor will accept for the potential across it to change 1 volt. A coulomb is 1 ampere second...
) capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
. The modern ANSI/TIA-968-B specification (August 2009) defines 1 REN as an impedance
Electrical impedance
Electrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...
of 7000Ω at 20Hz (type A), or 8000Ω from 15Hz to 68Hz (type B).
Maximum REN loading
The total REN for a subscriber's line is simply the sum of the RENs of all deviceInformation appliance
In general terms, an information appliance or information device is any machine or device that is usable for the purposes of computing, telecommunicating, reproducing, and presenting encoded information in myriad forms and applications....
s connected to the line; this number expresses the overall loading effect of the subscriber's equipment on the central office ringing current generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
. The local telephone company
Telephone company
A telephone company is a service provider of telecommunications services such as telephony and data communications access. Many were at one time nationalized or state-regulated monopolies...
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. For example, Call waiting
Call waiting
Call waiting , in telephony, is a feature on some telephone networks. If a calling party places a call to a called party which is otherwise engaged, and the called party has the call waiting feature enabled, the called party is able to suspend the current telephone call and switch to the new...
and caller ID
Caller ID
Caller ID , also called calling line identification or calling number identification or Calling Line Identification Presentation , is a telephone service, available in analog and digital phone systems and most Voice over Internet Protocol applications, that transmits a caller's number to...
are often affected by high REN. 20th century equipment tends to contributes larger REN than new equipment. In extreme cases, the telephone service provider may temporarily disconnect an overloaded line to reduce load.
Some analog telephone adapters for Internet telephony require analog phones with low REN, but researching RENs online is difficult because manufacturers and sellers seldom provide that information. However, the AT&T 210 is a basic phone that reputedly has a REN of 0.4.
International usage
In the United KingdomUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
it is called the ringer equivalence number and a maximum of 4 is allowed on any British Telecom (BT) line.
In Canada it is called a Load Number (LN); which cannot exceed 100. (The LN of each device represents the percentage of total load allowed).
In Europe 1 REN used to be equivalent to an 1800Ω resistor in series with a 1 µF capacitor. The latest ETSI specification (2003-09) calls for 1 REN to be greater than 16 kΩ at 25 Hz and 50 Hz.