The simplest and oldest type of mechanical timer is the hourglass - which is also known as 'the glass of the hour' - in which a fixed amount of sand drains through a narrow opening from one chamber to another to measure a time interval. The mechanical kitchen timer was invented in 1926 called a fan fly that spins against air resistance low-precision mechanical egg-timers are sometimes of this type. Each swing of the wheel releases the gear train to move forward by a small fixed amount, causing the dial to move steadily backward until it reaches zero when a lever arm strikes a bell. They function similarly to a mechanical alarm clock the energy in the mainspring causes a balance wheel to rotate back and forth. Manual timers are typically set by turning a dial to the time interval desired turning the dial stores energy in a mainspring to run the mechanism.

Mechanical use clockwork to measure time. Time switches, timing mechanisms that activate a switch, are sometimes also called 'timers'. Most timers give an indication that the time interval that had been set has expired. Working method timers have two main groups: hardware and software timers. A simple example of the first type is an hourglass. The word 'timer' is usually reserved for devices that counts down from a specified time interval, while devices that do the opposite, measuring elapsed time by counting upwards from zero, are called stopwatches. Timers can be categorized into two main types. A timer is a specialized type of clock used for measuring specific time intervals.

Short timer clock