My favorite alarm clock to wake up by is the Westclox Moonbeam. Its alarm is a flashing light, followed by a sound. The original model, introduced in 1949, would start buzzing obnoxiously if the flashing light was not shut off within about 15 minutes. The modern reproduction version has a 5 minute snooze feature and rings a bell if you do not shut off the alarm after about 10 minutes.