A husband and wife decided they needed to use "a code" to indicate
that they wanted to have sex without letting their children in
on it. They decided on the word "typewriter."
One day the husband told his five year old daughter, "Go tell your
mommy that daddy needs to type a letter." The child told her
mom what her dad said and her mother responded, "Tell your daddy
that he can't type a letter right now because there's a red
ribbon in the typewriter." The child went back to tell her father
what mommy had said.
A few days later the mom told the daughter, "Tell daddy that he
can type that letter now."
The child told her father, and then returned to
her mother and announced, "Daddy said never mind with the typewriter,
wrote the letter by hand."