When Edison was a boy of fifteen, he worked as a telegraph operator. He had to be on duty at night from 7 o’clock in the evening till 7 o’clock in the morning. But at night there was never much work and the telegraph operators usually slept. So the boss ordered each operator to give a signal every hour to show that he was awake. Edison’s signals always came at the same time at the beginning of each new hour. That surprised the boss. So one night he sent an inspector to see how well the boy was working. When the inspector opened the door he saw Edison sleeping in his chair. The inspector was going to shake the boy when he saw a block with a mechanism on the table near the telegraph apparatus. He waited to see what would happen. When the hand of the clock pointed to the hour, the mechanism began to work and sent a signal. The inspector went up to the boy and shook him. Edison awoke. He was told that he had lost his job. This story explains why the first of Edison’s many inventions was never patented.