Broadband and House alarm modem conflict

[#1]

Finally joined the 20th century and got broadband. Only now we find that the dial up modem on the house alarm doesnt work correctly. When the alarm is activated it should contact us, but now it doesn't. The only way round it so far is to unplug the DSL cable, which isnt ideal but the house is more important than broadband. Any ideas gratefully recieved.

[#2]

Contact your alarm system maintainer. These days they all know how to configure alarm diallers properly to work with broadband and fit appropriate filtering etc.
You should have done this before ordering, but it's easy to fix.