Telephone
A telephone is defined as an instrument that facilitates the simultaneous transmission and reception of human voice. Telephones are not very expensive and are easy to operate, offering immediate and personal communication. The word telephone is derived from two Greek words, 'tele' which means 'far', and 'phone', which means 'sound'. Since its invention, the telephone has also helped send documents by fax and it is the basic infrastructure on which the internet is built.
History of telephone: Before the invention of the telephone, the telegraph was used for communication. It was a simple electrical circuit that stretched many miles, usually along a railway line. Messages were sent down the telegraph line in the form of electrical bursts. However, telegraphs were slow, tedious to use and required people to learn Morse Code. Telephone changed all of this.
In 1876, Alexander Graham Bell sent me first words by telephone. Later in the year, he also made the first long-distance call to his assistant who was 2 miles away. He was the first person to be granted a United States patent for the telephone. Within seven years of the invention of the telephone, telephone exchanges were established in Bombay (now Mumbai), Madras (now Chennai) and Calcutta (now Kolkata). By 1896, the telephone instrument was improved upon by Thomas Watson, Emil Berliner and Thomas Edison among others. By 1915, people could make transcontinental calls - the first call was made by Dr Bell in New York to Mr Watson in San Francisco, USA. By 1927, people could make International calls - the first was made across the Atlantic Ocean. In the late 1970s the first cell phones appeared. Around the same time, fax machines became common too. They used telephone wires to send words and images.
How telephone works: The traditional telephone relies on telephone wires to transmit sound. It consists of a handset and a base that are joined by a cord. The user holds the handset while talking - one end of it has a microphone to speak into and the other end has a loudspeaker to hear the user on the other end. The wire in the base connects the telephone to an electric current.
When a user talks into the handset, the microphone converts the sound of the user's voice to an electric signal. The signal is sent out by the base through its wire. The signal's path from there depends on where the call is going. It either remains as an electric current, passing through wires and cables, or travels through thin glass fibres in the form of light. Sending information in this manner is called fibre optics. The signal can also be converted to radio waves and sent through the air via antennas and satellites. When the signal reaches the telephone of the other user, the loudspeaker converts it back to the sound of a voice.
Different types of telephones:
● Cordless telephone: A cordless telephone does not have a cord connecting the handset and the base, which allows the user to walk or move while talking. It uses electric signals and radio waves to operate. The base receives the call in the form of an electric signal and turns it into radio waves. The base then sends the waves through the air to the handset using the antenna. The handset's antenna picks up the waves and then the handset converts the waves into sound.
● cell phone: Cell phones, also known as cellular phones or mobile phones, operate over a wider area and are more convenient than cordless phones. They make and receive calls through radio waves. This works with the help of cell phone companies. They divide an area into sections called cells. Each cell has a tower that can receive and send radio waves. If the person on call moves from one cell phone to another, the call also switches from one tower to another. So essentially, the cell phone can work anywhere the cell company has a network. The phone transmits a special signal when it is turned on. This signal tells the network where to direct the calls that the phone receives. Today, cell phones can do many things other than calling, like sending text messages, taking photographs, playing music, getting information from the internet and emailing. Smartphones can also run applications or apps that allow people to play games, shop, read, view maps, manage calendars and perform many other tasks.
