DH+ is Data Highway Plus Industrial Local Area Network from AB.
The Data Highway Plus (DH+) network is a local area network that is very simple to implement. It is designed to provide simple communication between AB's PLCs, SLCs and PCs.
The Data Highway Plus network allows connection to a maximum of 64 devices per link (although 15 or fewer nodes are recommended per link), including:
PLC-5 and SLC 5/04 programmable controllers
Color graphics systems
Programmable RS-232-C/RS-422 devices
A network can be configured with 99 links. With a multi-link network, more nodes in the network are possible. By placing nodes in the proper link with some nodes and separate from other nodes, the efficiency of message delivery can be improved. Using simple twisted-pair wiring, DH+ can be configured as a trunk-line drop or a daisy-chain topology.