The mechanical automatic irrigation timers are very simple to use. Generally they are used for sprinklers or very small watering systems where a higher level of control is not needed. They are usually clock work based so you simply dial in the period of time or the quantity of water and hey presto away it goes. When it has completed its watering cycle it switches itself off (great for the people who forget to do this).

The Gardena timer is clockwork timer.

Beware of the type that measure the quantity of water going through as often they do not work with drip systems as the water use is too low for correct operation.