However, clocks have actually been around for about 600 years. The first mechanical clocks appeared sometime in the 14th century, typically the huge ones set in towers like Big Ben (only it was made in 1858). By around 1620, Household clocks became common, and some of them even had alarms. Alarms have a "cam" that rotates every 12 hours. A lever falls into a notch which releases a train of gears that drives a hammer onto a bell over and over until it runs down. Later they had shut-off control which was a lovely addition, don't you think?
A lantern clock from about 1620 has an alarm set disc on front of the dial. A grandfather clock circa 1690 has a 30 hour hanging timepiece alarm.Levi Hutchins of Concord, New Hampshire has been credited as the inventor of the first alarm clock in 1787. However, his alarm clock has been clearly predated by the German and English. When English clockmakers emigrated to the United States, they brought this skill with them.
Simon Willard of Grafton, Massachusetts, crafted alarm time timepieces called “lighthouse clocks” in the 1820's. There are also American wooden works shelf clocks which were made ain the 1820's and 30's which have alarms similar to many brass movement shelf clocks of the 1840's.
For further reading about alarm clocks from the 1500's, see “The Clockwork Universe, German Clocks and Automata 1550 - 1650,” Maurice and Mayr, 1980, Smithsonian, Neale Watson Academic Publications, New York. The book “Early English Clocks” by Dawson, Drover and Parkes, Antique Collectors Club, 1982, documents some early alarm clocks.