1. The Telephone By: Adrian Iglesias & Angel Ferrer

2. The telephone is a telecommunications device that is used to transmit and receive sound, usually two people conversing but occasionally three or more. It is one of the most common household appliances in the world today. Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost anyone.

3. In the year 1854, the French inventor Charles Bourseul raised in an illustrated magazine of the time the possibility of using vibrations caused by the voice Some years later, physicist and professor Johan German Philipp Reis invented a musical instrument, transmitting distance In 1876, having discovered that to transmit human voice could only be used a continuous stream, the inventor of U.S. origin Scot Alexander Graham Bell patented and built a few hours before his compatriot Elisha Gray the first phone capable of transmitting and receiving human voice with their whole quality.

4. In terms of the phone itself, can draw several things: The introduction of the microphone coal, which increased considerably the power emitted, and therefore the maximum range . The antilocal device in order to avoid disruption in the hearing caused by noise from the local environment where the phone is installed. The dial pulses through the so-called disk mark. multi-tone dialing. The introduction of the electret microphone or electret, condenser microphone, used in virtually all modern appliances, which significantly improved sound quality.

5.  A phone is made up of two circuits that work together: the circuit of conversation, which is the analogue dial and the circuit, which is responsible for dialing and call. Both signals such as voice dialing and call (signalling), as well as food, they share the same pair of wires, this is often referred to as "signaling within the band (voice)."

6. thank you all for your cooperation THE END