Questions tagged [telephone]

A telephone, is a telecommunications device that converts sound into electronic signals suitable for transmission via cables

A telephone, or phone, is a telecommunications device that converts sound into electronic signals suitable for transmission via cables or other transmission media over long distances. First patented in 1876 by Alexander Graham Bell and further developed by many others, the telephone was the first device in human history that enabled people to talk directly with each other across large distances. It rapidly became indispensable to businesses, government, and households, and it is now among the most widely used appliances in the developed world. The word telephone has been adapted into the vocabulary of many languages. It is derived from the Greek: τῆλε, tēle, far and φωνή, phōnē, voice, together meaning distant voice.

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Amplification before tubes and transistors were invented

Telephones are older than vacuum tubes and of course transistors. How was signal amplification done? I mean the technology, not the details. EDIT Some additional informations that I should have given at the beginning : The question is…
andre314
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Why do devices stop operating properly in extreme cold?

I have noticed that a lot of smart phones say that they won't operate under -4 degrees F (-20 degrees C). Can anyone explain to me what happens when the phones get cold that stops them from operating?
Sean Moriarty
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How were four wires replaced with two wires in early telephones?

In this video, when A wanted to talk to B, a microphone was connected to a distant speaker using two wires (A → B). When B talked to A, a copy of above was used in the other direction (B → A) using two more wires. This required four wires: But then…
across
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Why do PBX systems use -48 V?

It seems common that PBX and other telephone hardware use a positive-ground power supply, where the "hot" line is at -48v. What's the reason for that?
Carl Raymond
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Why do push button telephones use dual-tone for signalling?

Here is a related information from wikipedia: For touchtone service, the signal is a dual-tone multi-frequency signaling tone consisting of two simultaneous pure tone sinusoidal frequencies. Above shows that if one pushes number 1 he sends…
user16307
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Cell Phone as Microcontroller

I have a couple of cell phones laying around, one of them being this one: http://www.gsmarena.com/sony_ericsson_elm-3057.php Is possible to clear the flash memory and replace it with a bootloader and then upload arduino sketches or pic32…
Harry Svensson
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How does a UK analogue telephone detect that the caller has hung up (disconnected)?

Scenario This is a question regarding the design of UK analogue telecommunications equipment and the consequent design impact that is necessary for a router duplicating those signals. It is asked so that I can liaise with the designers of the router…
user2834566
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Unplugging a router from the wall socket

When the internet appears to have crashed, the service provider invariably gives this advice as a first line remedy: unplug the router from the wall socket, then wait 5 minutes, then plug it back in. Many times this remedy works. Question: Why does…
Gayot Fow
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Control the hardware of an old phone using a Raspberry PI

I have a very old phone (60 years old) and I want to control its part using a Raspberry PI: Microphone & speaker from the head set The bell The dial wheel I have the electric circuit but don't recognise all of the parts. My question is now how I…
Besi
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How does a signal travel down a telephone wire?

Supposing a computer gets data over telephone wire, it has to send/recieve signals, but how do things work? Does it use analog signal or a digital bits? How does it send/recieve "1"s and "0"s?
cursious10
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Wiring up old phone ringer to arduino

I just obtained an old rotary phone at a garage sale. I am working on hooking it up to an arduino project, and I was able to get the dial and hook switches figured out pretty easily. I cannot really figure out how the ringer works, or how to wire it…
captncraig
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Could someone help me understand this simple circuit?

This is a single-wire earth-return telephone system used in cave rescue communications. simulate this circuit – Schematic created using CircuitLab The ground is a metal casing to make contact with the users hand. Line is clipped to an exposed…
Jake
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How does the telephone's keypad work?

I disassembled some old telephone and mobile phone. Every keypad is different, and yet, all of them have those "spirals" (see the image below) under the button or something similar. What I don't understand is how those "spirals" can put in contact…
Tripola
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Why are modern telephone lightning arrestors less prone to (rectification) RFI problems than old ones?

I was reading about telephone lightning arrestors in my ARRL RFI Book (first edition, copyright 1998), in chapter 9 "Telephone RFI" (by Pete Krieger, previously WA8KZH, now K8COM) and on page 9.6, the following is stated (emphasis mine): The…
MicroservicesOnDDD
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How do I connect an Arduino to a landline?

How do I connect an Arduino to a landline telephone wall outlet? I'm thinking of home automation, something like: I call my house, and after a few rings the Arduino picks up the phone The Arduino somehow (modem? synthetic voice?) tells me the house…
davidcary
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