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Alexander Graham Bell
Alexander Graham Bell was born in Scotland on March 3, 1847.
In 1870, he emigrated with his family to Canada, and two years later they moved to Boston. Bell's father and grandfather were both phonetics experts, who instructed those with speech impediments and conducted research on the human voice.
Young Bell also taught, and combined the two fields he most enjoyed, music and speech. In 1873 he was awarded a professorship at Boston University, where he researched the science of speech.
There was also a personal side to his interest in speech - both his mother and his wife had lost their hearing in childhood.
Bell, at the age of 29, revolutionised communications when he invented the telephone - the most profitable patent ever registered. The telephone is based on the ability to transmit vibrations originating in voice waves from one location to another using electric currents.
The first telephone conversation was held between Bell and Tom Watson, his assistant, who was sitting in a room distant from Bell, when he heard Bell's voice call, "Come here, Watson, I wish to speak with you". Alexander Graham Bell said of himself: "An inventor cannot help but invent, just as he cannot help thinking and breathing". Thirty different patents are registered in Graham's name, including voice transfer using light beams, a pyramid shaped kite capable of carrying a man, and a hovercraft which attained a world record for speed for that kind of vehicle in 1919. Most of all, Bell preferred to define himself as a "teacher of the deaf".
Bell died on August 2, 1922, at the age of 75.
Thomas Alva Edison
Thomas Alva Edison was born on February 11, 1847 in the town of Milan, Ohio, USA. Edison was an active, curious child. His formal education ended at the age of 7, after only three months at school. Thanks to his mother, a former teacher, he learned to read and developed an interest in books on a variety of subjects.
He began his business and science career at the age of 12, and when he was 23, he developed his first invention - an automatic telegraph system.
In 1877, Edison announced his invention of the phonograph by which sound could be recorded and reproduced, and thus the era of sound recording began.
At the age of 31, he began working on a safe, inexpensive electric light bulb, to replace the gas and kerosene lamps which were in use at that time.
In 1879, after a year of trials and experiments, his "invention" lighted the dark skies of Menlo Park, New Jersey (the location of his laboratory) for several hours.
His invention was an incandescent light bulb with a carbonized cotton thread for which he will always be remembered.
He also contributed to the development of the first large electric power station which began operating in 1882, encouraging widespread use of electricity.
Over 1,000 patents are registered in Edison's name, including the alkaline battery, a discovery known as the Edison Effect which led to the invention of the electronic tube, the silent movie projector (predecessor of current cinema), and others.
Thomas Alva Edison, a great inventor, died on October 18, 1931 at the age of 84.
The Souvenir Sheet, issued in honour of the 150 year anniversary of the birth of Thomas Alva Edison and Alexander Graham Bell, is dedicated to the Asian International Stamp Exhibition to be held in Hong Kong in 1997.
The stamp on the right hand side shows Alexander Graham Bell dedicating the New York - Chicago telephone line in 1892. The stamp on the left hand side shows Thomas Alva Edison in his laboratory with a light bulb.
The background of the sheet shows a photograph of Hong Kong by night (photo by Gidi Marinsky), together with an electric pole, developed in Israel.
The lower right corner of the sheet shows the logo of the Hong Kong '97 Exhibition. The upper left corner of the sheet shows the logo of the Israel World Stamp Exhibition '98.
