right adjust data entered in a field when the operator exits the field. Signed numeric reserves the rightmost position of a field for a sign – blank for positive or '-' for negative. Terminal status lights On a 5251 type terminal featured five status lights on the front of the unit: System Available light: If lit, this terminal is connected to the host system and is receiving information from it. Message Waiting light: Other users, and the system itself, can send messages to workstations. If lit, there is at least one message that has not been seen yet. When a program ends or when the user signs on, the message(s) will be shown. Insert light: The Insert key has been pressed. Characters after the cursor will shift right when text is keyed. Press Insert again to cease Insert Mode. Caps Lock light: The Caps Lock key has been pressed. Keyboard Shift light: The Shift key is being pressed. 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