how to reset code on concept 6 with out original code?

Start by downloading the install/user manual,a quick google search will turn one up.
The user default code is in there,along with specific info you need.
Start by replacing the battery with mains disconnected,

connect the new battery and key in the (user default code),its in the manual.
If you can silence the alarm with the code,then you may need to reprogramme.

If the alarm doesn't silence,then get a pro in,but honestly,its old and upgrading is another option worth considering.

Don't !! remove the panels cover with the mains connected.

no name
April 2012