The 1784-KTx interface card is also related in functionality of the 1784-KTXD, and 1784-KTS.  It is an ISA  half-sized interface card that fits into a 16-bit ISA or EISA slot.
Operation of the he 1784-KTX and -KTXD cards:

• Talks with any stations on Data Highway networks which include PLC-2, PLC-3 and PLC-5s & SLC 5/04s on DH+.  It can also communicate with SLC 5/01, SLC5/02, and SLC 5/03 with the 1784KA5 module.
• Talks on DH-485 with SLCs.
• The 1784-KTX acts as a remote I/O scanner.

The 1784-KTx functionalty includes diagnostics, management and transmission of data.

Allen-Bradley’s RSLINX/ LOGIX software is handled through the dual-port memory which manages data transmission and reception.

The most popular network that the 1784-KTX can communication is DH+. Data Highway (DH) and Data Highway Plus are industrial bus protocols developed by Rockwell Automation/Allen Bradley.

AB DH+ Overview:

Data Highway Plus is a factory automation network that provides simple communication between industry popular AB PLC-5s, SLC 5/04s, Panelviews and other devices. Both DH and DH+ have 64 nodes and the communications protocol used to interconnect the Network link and a PC is called DF1.

DH+ uses a trunk cable that runs up to 10,000 ft., and drop cables to each node that extend to 100 ft.  It is made up of peer-to-peer communication and each node bids to be the the Floating Master.

DH+ is most popular in smaller factory  networks using peer-to-peer communication that is implemented by Token passing.  Voltages is 8 to 12 volts peer-to-peer; and the bus is +/- 200mV sensitive over the two differential lines. Each node on the bus is transformer coupled onto the bus. The bus should be terminated to 150 ohms at each end of the bus. All messages on the bus are either a command or a reply.

Also developed by Rockwell Automation/Allen Bradley is the Data Highway 485 protocol a local area network design for factory-floor applications. DH-485 allows for the connection of up to 32 devices, including controllers, color graphics systems and PCs.

You can connect the Interface Card to classic PLC-5 processors, enhanced PLC-5 processors, SLC 5/04 processors and 1756 ControlLogix DH+/RIO.

Source: www.ab.com