science

Last-call return

Last-call return is a science 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 Last-call return rather than just read about it. In short: Last-call return, automatic recall, or (on PBX and centrex service) camp-on, is a telecommunication feature offered by telephony service providers to subscribers to provide the subscriber with the telephone number, and sometimes the time, of the last caller. The service may also offer the facility to place a call to the calling party.

Key takeaways

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

Reference excerpt

Last-call return, automatic recall, or (on PBX and centrex service) camp-on, is a telecommunication feature offered by telephony service providers to subscribers to provide the subscriber with the telephone number, and sometimes the time, of the last caller. The service may also offer the facility to place a call to the calling party. The general public tends to refer to the service by the telephone feature code, the telephone number it has in their country; for example, in North America, this is *69, while in the UK, it is called 1471. The New York Times described Call Return in 1992 as a new service. It can be paid for per-call or subscribed to monthly.

Feature code The number for this facility varies with country and provider:

United States and Canada: Vertical service code *69; 1169 on rotary phone/pulse dial telephones. The prompt voice behind most U.S. AT&T implementations of this feature is Pat Fleet. Where available, it is offered on a per-call charge (typically 50¢) or an unlimited-use monthly subscription for a few dollars. Australia: *10# for Telstra services or *69 on Optus HFC Telephony network. This only allows one to return the last unanswered call, and can cost 35 cents per use. France: 3131 Israel: *42 Japan: 1361 to get number, 1363 to call back. United Kingdom: 1471 (also used in Gibraltar, Ireland, Isle of Man, Channel Islands, and the Falkland Islands) In the UK, after dialing 1471, the caller can press "3" to automatically return the call. Previously free, since August 2004 the return call service incurs a charge. The service provider may also offer a facility by which the calling party can prevent their number being revealed to the called party, either permanently or on a per-call basis. This is achieved by prefixing the dialed number with:

Australia: 1831 on landlines and mobile phones, or #31# from a mobile United Kingdom, Ireland, Isle of Man, and Channel Islands: 141 on landlines and #31# on mobiles United States: *67 Sweden: #31# Conversely, to send the caller number on a line where the number is normally withheld, the following prefixes can be dialed:

Australia: 1832 on landlines, or *31# from a mobile Ireland: 142 United Kingdom: 1470 (also used in Gibraltar and the Channel Islands) United States: *82 Philippines *999 In Gibraltar and formerly in Ireland, ex-directory or unlisted numbers are withheld by default. In Germany, most contemporary telephones have a specific button functioning as call return, which is an internal function of the telephone itself (the number of the last caller is stored inside the phone at the time of that last call) and thus doesn't have a numeric code. In Canada, the feature is commonly marketed by telephone companies as a combination of two features:

Call again, a form of automatic ring back, allows a caller, on reaching a busy signal, to hang up, dial a special code, and be called back automatically when the called number is no longer busy, usually with a limit of 30 minutes. Call return allows a customer to dial a code that identifies the last incoming call. On some types of central office equipment, it announces the number and offers the call-back option; on others, it simply attempts a connection without an announcement.

See also Vertical service code Telephones portal

References

Worked examples

Example 1 — a first encounter with Last-call return

Start with the simplest possible case. Write down what Last-call return claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Last-call return 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 Last-call return 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 Last-call return

In research: Last-call return appears in science 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 Last-call return 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: Last-call return is common in secondary-school and first-year university syllabi. It links to neighbouring topics Calling features, Telephone service enhanced features, Teletraffic, so understanding it makes those chapters shorter.
In everyday life: Look for Last-call return 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 Last-call return in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Last-call return 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 Last-call return out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Last-call return in simple terms?

Why does Last-call return matter?

Because it connects several science 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 Last-call return?

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 Last-call return.