3270 emulator

As the original 3270 series terminals were connected to the host computer through a display controller (cluster controller)[a] using coaxial cable, emulators originally required channel (rare), coax or synchronous communication adapter cards to be installed in the PC.

Today, many emulators communicate with the mainframe computer through a TN3270 server[b] using the TN3270 (RFC 1576) variant of the Telnet (RFC 495) protocol common on TCP/IP networks including the Internet, so special hardware is no longer required on machines with Internet access.

Several vendors offered both coax and communications attached 3270 emulators and TN3270 clients as part of the same product.

This is common in protocol converters or other situations where performance justifies the higher cost.

Some 3270 simulators use a coax adapter such as the Irma board to connect to a cluster controller.

A terminal window showing white text on a black background. An ASCII art logo reads MUSIC/SP and is captioned below as Multi User System for Interactive Computing / System Product.
A TN3270 client running on Windows
An interface card for running the 3270 emulator on an IBM PC.
DCA IRMA II ISA for PCs.