technician code; where did my sound go?

I understand that there is a technician code I can obtain that wil allow me to change my motion sensor to arm when at home at bedtime, but I cannot find it.  Could someone repost?  Also, I changed my sounds after reading a post, setting different sounds for the most used doors so I would know which door was opened.  Now, there is no sound.  I did not silence anything.  Help!