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Defining a city using cell-phone data

Humans are becoming more urban, with more than half of the world's population now living in cities. This rapid growth poses unique challenges to both the study and governance of cities—a challenge made harder because we ...

Chatbot guides women through post-prison challenges

Most women leaving prison face profound disadvantages and rarely have access to the resources needed to settle back into the community. Seemingly simple tasks such as obtaining replacement identification documents or opening ...

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Telephone

The telephone (from the Greek: τῆλε, tēle, "far" and φωνή, phōnē, "voice") is a telecommunications device that transmits and receives sound, most commonly the human voice. It is one of the most common household appliances in the developed world, and has long been considered indispensable to business, industry and government. The word "telephone" has been adapted to many languages and is widely recognized around the world.

The device operates principally by converting sound waves into electrical signals, and electrical signals into sound waves. Such signals when conveyed through telephone networks — and often converted to electronic and/or optical signals — enable nearly every telephone user to communicate with nearly every other worldwide. Graphic symbols used to designate telephone service or phone-related information in print, signage, and other media include ℡, ☎, ☏, and ✆.

This text uses material from Wikipedia, licensed under CC BY-SA