How does a telephone work?
A traditional landline telephone system, also known as “plain old telephone service” (POTS), commonly handles both signaling and audio information on the same twisted pair of insulated wires: the telephone line. Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication. The signaling equipment consists of a bell, beeper, light or other device to alert the user to incoming calls, and number buttons or a rotary dial to enter a telephone number for outgoing calls. A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference (EMI) and crosstalk than an untwisted pair.
A traditional landline telephone system, also known as “plain old telephone service” (POTS), commonly handles both signaling and audio information on the same twisted pair of insulated wires: the telephone line. Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication. The signaling equipment consists of a bell, beeper, light or other device to alert the user to incoming calls, and number buttons or a rotary dial to enter a telephone number for outgoing calls. A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference (EMI) and crosstalk than an untwisted pair. A calling party wishing to speak to another party will pick up the telephone’s handset, thus operating a button switch or “switchhook”, which puts the telephone into an active state or “off hook” by connecting the transmitter (microphone), receiver (speaker) and related audio components to the lin
The telephone was created through the cross-pollination of two fields of study – electricity and acoustics. Although the invention of the telephone is usually credited to Alexander Graham Bell, many inventors were working on the problem throughout the 1860s and 1870s, most notably Elisha Gray, who filed a patent application for the same device only a few hours after Bell did. Although the basics of electricity were known by the 1830s, nobody suggested transmitting speech electrically until 1854. The telephone was finally invented on March 10, 1876. Into it were spoken the famous words, “Mr. Watson, come here, I want to see you.” The telephone operates on simple principles. A telephone mouthpiece contains a thin metallic coating separated from an electrode by a thin barrier (today we use plastic) which connects to a wire carrying an electric current. When a person speaks into the mouthpiece, the acoustic vibrations from her speech push the metallic coating slightly closer to the electro
The first telephone was made with the knowledge that sound gave off waves due to vibrations, like the ripples in water. These sound waves were copied over onto carbon grains, which an electric current traveled through to make the grains vibrate. However, the different patterns of the grains altered the resistance of the grains against the electric flow. In this way the sound made more or less current flow in the circuit. These currents were in proportion to the sound waves that first entered. At the other end was a coil of wire within a magnet attached to a diaphragm. The variations in current caused the wire to move in the magnetic field. These vibrations move air, and that reproduced the sound at the other end!
