Atari 800 - keyboard modes?

Hi all,

Embarrassed to have to post this, but nowhere can I find an answer elsewhere. My Atari 800 has been repaired and boots up fine, either into Memo Pad or Basic, with the cartridge on.

All I can get when I type anything, is 'control' characters (or other words, small 8x8 graphics. What on earth is the key combination to toggle back to normal, alphanumeric mode.

Thanks

Matt