U stands for IC integrated chip Z represents some special diode S may represent some switches what, do not know the specific ISO is the above isolation device VR is usually variable potentiometer (adjustable resistance) JP is often a jumper These labels may change because of the designer ~ there is no very strict meaning that must be so marked, When I design PCB, the jumper is often only marked J, and the chip weight is not represented by U, but by IC1 and IC2.
U stands for IC integrated chip Z represents some special diode S may represent some switches what, do not know the specific ISO is the above isolation device VR is usually variable potentiometer (adjustable resistance) JP is often a jumper These labels may change because of the designer ~ there is no very strict meaning that must be so marked, When I design PCB, the jumper is often only marked J, and the chip weight is not represented by U, but by IC1 and IC2.