Terminal keyboards often have a number of keys that one doesn't find on a PC keyboard. Few (if any) actual terminals will have all of these keys and most will have additional keys not listed here. Some have a large number of special purpose keys such as terminals made for use with cash registers. There are often many more key meanings than shown here since these keys often have extended meanings when used in conjunction with other keys (such as shift and control).
- BREAK sends a very long 0 bit (space = +12 V) of duration 300 to 700 milliseconds to the host. The host may interpret this as an interrupt if stty has set brkint or ignore it if ignbrk is set.
- NO SCROLL stops the screen from scrolling like ^S does. Depressing it again resumes scrolling. Uses flow control signals to do this.
- REPEAT if held down with an other key, forces repeated output of that other key even if the auto-repeat option is set to off.
- LINE FEED sends the line feed character ^J to the host. Seldom used.
- SET-UP allows the manual configuration of the terminal via menus. Sometimes purposely disabled by putting a block under it so it can't be pressed down. Sometimes another key such as shift or control must be pressed at the same time. See Getting Into Set-Up (Configuration) Mode.
- LOCAL disconnects the terminal from the host. In local, what one types goes directly to the screen. Useful for testing.
- RETURN is the same as the "enter" key on a PC. It usually sends a carriage return to the host which normally get translated to a new-line character by the host's device driver. On some terminals it may be set up to send something else.
- F1, F2, ... or PF1, PF2, ... are function keys which usually may be programmed to send out a sequence of bytes (characters). See Function Keys