Telephone

Telephone An instruments that transmits the spoken word by means of electrical impulses through wires. Alexander Graham Bell invented the telephone in the united states in 1876. When you speak into the transmitter of the telephone, the sound waves vibrate a diaphragm.

This presses against grains of carbon, whose electrical resistance varies according to the pressure upon it. An electric current passes through the carbon grains, and varies in strength according to the pressure exerted upon them by the vibrating diaphragm.

The Variable current signals thus set up travel to the receiver (earpiece) of the telephone of the person you are calling. There they pass through an electromagnet over which is located another diaphragm. The diaphragm vibrates in sympathy with the signals and reproduces the sounds that originally went into the transmitter.

And Now - Digital telephone generation, called Handphone.