How do I turn off Special Characters? When I type an "s", I get "ß".

While doing some data entry, I accidentally hit a combination of keys that now make an "ß" appear whenever I type "s" and an "Í" appear whenever I type an "S". (I am manually pasting each "s" in this topic.

I know how to turn on the special characters for one-time use, but how do I turn it off? Thanks for your help.