How to use a scantronic 9427????

I have a scantronic 9427 alarm on my house and I have never used it since moving in, as I don't have a user manual, etc. I do have the alarm code however I have tried to change it and it doesn't seem to work now.
Does anyone know how this alarm works?? What the symbols on the alarm mean and how I reset code, turn on, off, etc??
I would really appreciate any help.
Thanks in advance.

Sherry