[20] Circuit symbols for manual operation
The switching position of a directional control valve can be changed by various actuation methods. The symbol for the valve is accordingly supplemented by a symbol indicating the actuation methods shown, such as pushbuttons and pedals, a spring is always necessary for resetting. Resetting can, however, also be achieved by actuating the valve a second time, for example in the case of valves with hand levers and detents.
The various actuating methods possible are listed in DIN ISO 1219.