This character is a Other Symbol and is commonly used, that is, in no specific script.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+2406 forms with similar adjacent characters prevents a line break inside it.
The Wikipedia has the following information about this codepoint:
In data networking, telecommunications, and computer buses, an acknowledgement (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgment, or receipt of message, as part of a communications protocol. Correspondingly a negative-acknowledgement (NAK or NACK) is a signal that is sent to reject a previously received message or to indicate some kind of error. Acknowledgments and negative acknowledgments inform a sender of the receiver's state so that it can adjust its own state accordingly.
Representations
System
Representation (click value to copy)
Nº
9222
UTF-8
E2 90 86
UTF-16
24 06
UTF-32
00 00 24 06
URL-Quoted
%E2%90%86
HTML hex reference
␆
Wrong windows-1252 Mojibake
â†
Encoding: GB18030 (hex bytes)
81 37 83 36
RFC 5137
\u'2406'
Bash and Zsh inside echo -e
\u2406
C and C++
\u2406
C#
\u2406
CSS
\002406
Excel
=UNICHAR(9222)
Go
\u2406
JavaScript
\u2406
Modern JavaScript since ES6
\u{2406}
JSON
\u2406
Java
\u2406
Lua
\u{2406}
Matlab
char(9222)
Perl
"\x{2406}"
PHP
\u{2406}
PostgreSQL
U&'\2406'
PowerShell
`u{2406}
Python
\u2406
Ruby
\u{2406}
Rust
\u{2406}
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