You can type it at a terminal the same way you can write other low-ascii codes. For example record separator, 30, is ctrl-^ - you can type it in the terminal by the usual literal control char way, ctrl-v[1].

So for example at a Python prompt:

  >>> ord('^^') # typed ctrl-v ctrl-^ here
  30

(the low unprintable ascii codes correspond to certain ctrl combinations because ctrl-x is just the ascii code of x with the high bits masked off (i.e. & 0x1f) )

[1] custimizable in your terminal settings, see stty lnext ("literal next")