sixwheeledbeast's post in Texcom Expanders was marked as the answer
Hopefully you have a power supply in there somewhere.
3 Expanders without a bell at the end is already a fair amount of current.
Either way it's a good idea to use Low Current and/or SCB mode on the Bell, so you don't drag the expanders down.
Program Expander Input as Bell Tamper, wire Return to input.
Power from the Aux.
Trigger in an output programmed a Bell SAB
sixwheeledbeast's post in Texecom Premier 832 Addition was marked as the answer
Pointless doing anything without the engineers code, which they won't give to you as this puts there other customers at risk.
The panel also while it's a bit untidy, looks full so no room for additions.
Your better talking to your current maintainer.
sixwheeledbeast's post in Reson8 Gives Low Level Alarm When Main Siren Disconnected was marked as the answer
Skip the switch.
If you need to isolate it I am sure you can work out how to do so from the panel end, with no modifications.