IBM 5250
IBM 5250 is a family of block-oriented terminals originally introduced with the IBM System/34 midrange computer systems in 1977. It also connects to the later System/36, System/38, and IBM AS/400 systems, and to IBM Power Systems systems running IBM i. Components. 5250 devices can be directly attached to the host or communicate remotely using Synchronous Data Link Control (SDLC) at up to 9600bit/s. Devices can also be clustered or daisy-chained. In 1980 the 5250 system consisted of the following components: 5251/5252 format control. Field attributes also define the type of data the operator can enter  into a field, and specify other control information for the field. Terminal status lights. On a 5251 type terminal featured five status lights on the front of the unit: Historical origins. The 5250 is a block-oriented terminal similar to, but not compatible with, the IBM 3270. Robustly constructed, 5251 terminals weigh roughly . The devices generate an audible clicking sound as the user types, similar to the electric typewriters of the era. The 5250 data stream definition has been refined over time to include GUI elements such as pop-up windowing, check and option boxes, mouse handling, and pull-down  menus. The IBM 3180 added support for seven colors - pink, red, blue, yellow, green, white, and turquoise. A protocol called the IBM 5250 Data Stream interpreted field attributes such as blinking, non-display, high intensity, reverse image, underline, and column separators and was used in combination to create colors. Normal text was presented as green on a 3180 color terminal, but high intensity became white. Column separators became yellow. Blinking became red. Underlined text was presented as blue. High intensity blinking became pink. High intensity column separators became turquoise. The term "5250" now refers to the data stream itself. Few  physical 5250 terminals with their bulky twinax cables still exist, although they are occasionally still used to provide a "connection of last resort," hard-wired to the host computer. Today, it is more common to use PC or web-based terminal emulation packages that can interpret and display 5250 data streams. Telnet 5250. Telnet 5250, or TN5250 describes either the process of sending and receiving 5250 data streams using the telnet protocol or the software that emulates a 5250 class terminal communication via that process. TN5250 allows a 5250 terminal emulator to communicate over a TCP/IP network instead of  an SNA network. Standard telnet clients cannot be used as a substitute for TN5250 clients, as they use a different data stream format. Interfacing 5250 terminals with commodity hardware. An interface was created to connect to the Twinax port of a 5250 terminal and communicate with it like an AS/400 host. It currently provides VT52 emulation and a shell on the system to which the adapter is connected. List of IBM 5250 Twinax terminals. IBM 3179. The IBM 3179 exists as a 3270 and a 5250 terminal. IBM 3180. The IBM 3180 exists as a 3270 and a 5250  terminal. IBM 3196. 80x24 characters. Models: IBM 3197. Models: IBM 3477. Models: IBM 3486. Models: IBM 3487. Models: IBM 3488. Does not include an internal display. An external monitor is connected via VGA. IBM 3489. Does not include an internal display. An external monitor is connected via VGA.