Specifying Control-= as a string?

[Ken Manheimer]

is there any way to specify the one-character key sequence:

 [(control =)]

as a lisp string?

the strings "\C-=" and "\^=" complain about "Invalid modifier in string".

this question is mostly academic, at this point.  i was thinking about
using it key as a binding in a keymap, but eventually realized that
regular (non-window-system) ttys won't pass it as input.  though i've
given up on that, i'd like to better understand the story here, and am
curious about whether there's any way to express it as a string, or
whether it's just a bad idea in principle (BIiP).

thanks for any clues!

ken
http://myriadicity.net