Electronic – What do 3-digit reference designators mean


While looking at many circuit boards and schematics, I often notice that 3-digit designators are used, for example R101 instead of R1.

What do these digits actually mean? The numbers are not in sequence, for example only a single relay, K101 may be present, still numbered 101.

Best Answer

You should be able to figure out it looking at the device as whole. You can find such numbering in the devices with multiple boards, multiple physical or logical blocks in it. First digit may designate block #, other two (usually) designate component # in the block.