How telephones work, 1960's -- Film 1750 скачать в хорошем качестве

How telephones work, 1960's -- Film 1750

A technical explanation of how a telephone works using sound waves and electrical relay. Boy in uniform at a table listens to a tuning fork. Close up of his ear listening, the fork and animated sound waves. Boy makes a tissue paper and comb sound box and blows it. two schoolboys in a garden with two tin cans and a long string. Close up of the boy's ear and the tin can. Still of Alexander Graham Bell. Model of his original phone system. Explanation of Graham Bell's system with a magnet and diagram. Diagram of modern carbon granule microphone. Sound waves. Speech current. Diagram of a receiver. Superimposed two school boys talking to each other on the phone, you see both boys with a dividing line. Boys demonstrate simple system. Plastic grey dial phone. Demonstration of how the phones are linked with a telephone exchange. Women sit in row at a manual telephone exchange. Plugging in. Close up of plugs and woman with head set. Little girl talks to schoolboy. Line of operators with supervisor. Automatic exchange shown. Boy dials.