The ringer equivalence number (REN) is a

telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

measure Measure may refer to: * Measurement, the assignment of a number to a characteristic of an object or event Law * Ballot measure, proposed legislation in the United States * Church of England Measure, legislation of the Church of England * Mea ...

that represents the

electrical load An electrical load is an electrical component or portion of a circuit that consumes (active) electric power, such as electrical appliances and lights inside the home. The term may also refer to the power consumed by a circuit. This is opposed t ...

ing effect of a

telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...

ringer on a

telephone line A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or ot ...

. In the United States, ringer equivalence was first defined by U.S. Code of Federal Regulations, Title 47, Part 68, based on the load that a standard

Bell System The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over one hundr ...

model 500 telephone The Western Electric model 500 telephone series was the standard domestic desk telephone set issued by the Bell System in North America from 1950 through the 1984 Bell System divestiture. Millions of model 500-series phones were produced and were ...

represented, and was later determined in accordance with specification ''ANSI/TIA-968-B'' (August 2009). Measurement systems analogous to the REN exist internationally.

Definition

The ringer equivalence of 1 represents the loading effect of a single traditional telephone ringing circuit, such as that within the Western Electric

. The ringer equivalence of modern telephone equipment may be significantly lower than 1. For example, externally powered electronic ringing telephones may have a value as low as 0.1, while modern line-powered telephones, in which the ringer is powered from the telephone line, typically have a REN of approximately 0.8. In the United States, the FCC Part 68 specification defined REN 1 as equivalent to a 6930 Ω

resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...

in series Two-terminal components and electrical networks can be connected in series or parallel. The resulting electrical network will have two terminals, and itself can participate in a series or parallel topology. Whether a two-terminal "object" is a ...

with an (

microfarad The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base units ...

)

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...

. The modern ANSI/TIA-968-B specification (August 2009) defines it as an impedance of at (type A ringer), or from to (type B ringer).

Maximum ringer equivalence

The total ringer load on a

subscriber The subscription business model is a business model in which a customer must pay a recurring price at regular intervals for access to a product or service. The model was pioneered by publishers of books and periodicals in the 17th century, and ...

line is the sum of the ringer equivalences of all devices (phone, fax, a separate answerphone, etc.) connected to the line. This represents the overall loading effect of the subscriber equipment on the central office ringing

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

source. Subscriber telephone lines are usually limited to support a ringer equivalence of 5, per the federal specifications. If the total allowable ringer load is exceeded, the phone circuit may fail to ring or otherwise malfunction. For example,

call waiting Call waiting is a telephone service where a subscriber can accept a second incoming telephone call by placing an in-progress call on hold—and may also switch between calls. With some providers it can be combined with additional features such as ...

caller ID Caller identification (Caller ID) is a telephone service, available in analog and digital telephone systems, including voice over IP (VoIP), that transmits a caller's telephone number to the called party's telephone equipment when the call is ...

, and

ADSL Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. ...

services are often affected by high ringer load. Some

analog telephone adapter An analog telephone adapter (ATA) is a device for connecting traditional analog telephones, fax machines, and similar customer-premises devices to a digital telephone system or a voice over IP telephony network. An ATA is often built into a sma ...

s for

Internet telephony Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...

require analog telephones with low REN, for example, the AT&T 210 is a basic phone which does not require an external electrical connection and has a REN of 0.9B.

International specifications

In the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

a maximum of 4 is allowed on any

British Telecom BT Group plc (trade name, trading as BT and formerly British Telecom) is a British Multinational corporation, multinational telecommunications holding company headquartered in London, England. It has operations in around 180 countries and is th ...

(BT) line. In

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

a maximum of 3 is allowed on any

Telstra Telstra Group Limited is an Australian telecommunications company that builds and operates telecommunications networks and markets voice, mobile, internet access, pay television and other products and services. It is a member of the S&P/ASX 20 ...

Optus Singtel Optus Pty Limited (commonly referred to as Optus) is an Australian Telecommunications in Australia, telecommunications company headquartered in Macquarie Park, New South Wales, Australia. It is a wholly owned subsidiary of Singapore, Si ...

Line. In Canada it is called a ''load number'' (LN); which must not exceed 100. The LN of each device represents the percentage of total load allowed. In Europe 1 REN used to be equivalent to an 1800 Ω resistor in series with a 1 µF capacitor. The latest

ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...

specification (2003–09) calls for 1 REN to be greater than 16 kΩ at 25 Hz and 50 Hz.

References

* {{FS1037C *

ANSI The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...

/ TIA-968-B *

TS 103 021 Telephony equipment Equivalent units