mathematics

Ringer equivalence number

Ringer equivalence number is a mathematics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ringer equivalence number rather than just read about it. In short: The ringer equivalence number (REN) is a telecommunications measure that represents the electrical loading effect of a telephone ringer on a telephone line. In the United States, ringer equivalence was first defined by U.S.

Key takeaways

Ringer equivalence number belongs to mathematics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ringer equivalence number to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ringer equivalence number from memory before moving on to harder problems.

Reference excerpt

The ringer equivalence number (REN) is a telecommunications measure that represents the electrical loading effect of a telephone ringer on a telephone line. 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 model 500 telephone 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 model 500 telephone. 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 in series with an 8μF (microfarad) capacitor. The modern ANSI/TIA-968-B specification (August 2009) defines it as an impedance of 7000Ω at 20Hz (type A ringer), or 8000Ω from 15Hz to 68Hz (type B ringer).

Maximum ringer equivalence The total ringer load on a subscriber 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 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, caller ID, and ADSL services are often affected by high ringer load. Some analog telephone adapters for Internet telephony 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 a maximum of 4 is allowed on any British Telecom (BT) line. In Australia a maximum of 3 is allowed on any Telstra or Optus 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 specification (2003–09) calls for 1 REN to be greater than 16 kΩ at 25 Hz and 50 Hz.

References

This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. ANSI/TIA-968-B ETSI TS 103 021

Worked examples

Example 1 — a first encounter with Ringer equivalence number

Start with the simplest possible case. Write down what Ringer equivalence number claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ringer equivalence number before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ringer equivalence number ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ringer equivalence number

In research: Ringer equivalence number appears in mathematics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ringer equivalence number in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ringer equivalence number is common in secondary-school and first-year university syllabi. It links to neighbouring topics Equivalent units, Telephony equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Ringer equivalence number outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ringer equivalence number in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ringer equivalence number means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ringer equivalence number out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ringer equivalence number in simple terms?

Why does Ringer equivalence number matter?

Because it connects several mathematics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ringer equivalence number?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ringer equivalence number.