P1 is an asynchronous master-slave communication between what is known as a Field Cabinet (master) and the FLN devices (slaves). FLN stands for Floor Level Network. The master individually addresses the various slaves. A slave responds only if the master addresses it. Communication between the slaves is not possible.

A Field Cabinet can have several FLN ports. Up to 32 FLN devices (slaves) can be connected to each FLN port.