In bash `expect` script autogeneratedd with `autoexpect`, there is a `^G` - what does it signify?

In bash expect script autogen'd with autoexpect,I am invoking line completion with a [TAB] in a situation where line completion offers no completions nor changes the input line. The script excerpt looks like this:

send -- "dummyprog 1[TAB]"expect -exact "^G"

where I have replaced a literal tab with the character [TAB] for visibility.

The ^G, is literal. I can see nothing about ^G on the ubuntu man pages for expect or autoexpect.

Is it a terminal control character? Is it an artifact of the expect program? What is it?