decommissioning alarm

[mikeF00]

Hi, I'm trying to completely decommission my alarm system (by that I mean I don't want to use it again).
I've removed the fuse from the fused spur, but when I remove the battery terminals, the siren begins?. I guess the siren is getting its power supply elsewhere?
I've reconnected just the battery, but now there is now a continuous noise coming from the control panel now, as I guess the system is warning me that it is on battery power only.

Any ideas on what I have to do?

the system is a Securit 700L

 

[Handymanjo]

Ladder job ?

 

[Dazza Jones]

Your outside bell with have a battery inside it. Needs disconnecting.