What ␏ means
Use your editor’s Unicode character picker or insert command.
Ctrl+O is different: in compatible terminal notation, it sends SI’s underlying control; it does not insert ␏.
What does SI mean?
It returns text to its standard character set after Shift Out.
The ASCII text-encoding standard listed SI by 1963. Teleprinters—machines that printed received messages—used SI and its partner SO to switch between the ink colors on a two-color ribbon. In 1967, ASCII defined SI as returning to the standard character table. Later character-set standards used the pair to switch among sets of letters and symbols; VT100 terminals used SI to leave line-drawing characters and return to normal text.
The ␏ picture is a printable character used in debugging displays and data files to show where SI occurs. It is not the SI control byte: a terminal can process the control without displaying ␏.
Technical and diagnostic: it shows where otherwise invisible SI traffic occurs in debugging displays and data files.
Ctrl+O sends SI; ␏ is the printable picture, so protocol input needs the control itself.
Don't confuse it with
1Questions people ask
1Why does ␏ look different in different fonts?
It can: Unicode treats the diagonal lettering as an example, so a font may use another control-picture layout without changing the character.
How to type ␏
␏\240FCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.