If asked what was the most significant timekeeping invention of the last few centuries, most people would probably mention digital clocks, wristwatches or - if they were of a technical bent - atomic clocks. It's almost a certainty that few would want to dignify the humble alarm clock with that accolade, largely because alarm clocks are most often regarded with a baleful and hostile eye early in the morning from between the warm sheets of a very comfortable bed.

For many people the alarm clock has become something of a bete noir. It was with these people in mind that the baseball alarm clock was marketed in the early 1990s. To silence it one had to throw it hard against a wall. This proved therapeutic for alarmophobes, but it could also lead to back strain as you rummaged around under the bed late at night trying to find out where it had rolled to.

One of the earliest reminders of the passage of time was the candle. A candle was placed on a tin tray, and a nail was inserted into the wax at a given distance from the flame. When the candle burnt down far enough the nail would fall out and land on the tray with a clatter. However, this method had all the drawbacks associated with such a primitive measure of time - variable conditions, including the presence or absence of a draft and the qualities of the wax, could cause the candle to burn down faster or slower than expected. As a result it was difficult to gauge the precise position in the candle to insert the nail in order for it to fall out at the correct time.

Perhaps surprisingly, the idea of using mechanical clocks not just to measure the passage of time but to give audible warning that a certain time had arrived seems to have arisen not long after the clock first became a widespread domestic item. Certainly by the beginning of the 16th century clocks were being made that incorporated some form of alarm system within their mechanism.

The method of setting the alarm time in early clocks varied. Some English clocks made around 1620 had a disc set into the clock face that could be turned to select the required hour. The alarm mechanism used a cam that rotated once every twelve hours. It had a notch in it and this would be positioned so that an arm fell into it at the predetermined time. This set in motion an arrangement of gears that caused a hammer to repeatedly strike a small bell.

Modern alarm clocks are often battery operated but it is still possible to buy the familiar clockwork variety which is topped by two bells and emits a truly alarming sound to rouse you from sleep. This type of alarm clock was patented by the Seth Thomas Clock Company of Connecticut in the mid-1870s. We should probably be grateful to Mr Thomas for his innovation, which allowed the alarm to be set for any time: an alternative clock design, patented 100 years earlier, included an alarm that would only go off at 4 a.m.