Distributors are electrohydraulic elements that can perform the following functions:
- distribution function: they perform various hydraulic connections between pipes;
- adjustment function: they adjust the flow on the circuits made between the pipes.
Elements fulfilling only the first function are called directional distributors and must introduce minimal pressure losses between the pipes so as not to affect the efficiency of the transmissions to which they belong.
The elements that perform the adjustment function are called regulating distributors, and from the systems theory point of view, they are mechano-hydraulic amplifiers (the ratio between the controlled hydraulic power and the mechanical power required for the control is much higher than 1).