Advantech ADAM-5511 Manual page 317

Multi-drop RS-485 implies that there are two main wires in a segment.
The connected systems tap from these two lines with so called drop
cables. Thus all connections are parallel and connecting or discon-
necting of a node doesn't affect the network as a whole. Since
ADAM-5510/P31 systems use the RS-485 standard, they can connect
and communicate with the host PC. The basic layouts that can be used
for an RS-485 network are:
The last module of a segment is a repeater. It is directly connected to
the main-wires thereby ending the first segment and starting the next
segment. Up to 32 addressable systems can be daisychained . This
limitation is a physical one. When using more systems per segment the
IC driver current rapidly decreases, causing communication errors. In
total, the network can hold up to 64 addressable systems. The limita-
tion on this number is the two-character hexadecimal address code that
can address 64 combinations. The ADAM converter, ADAM repeaters
and the host computer are non addressable units and therefore are not
included in these numbers.