Arduino intruder alarm modification Answered
We have a professionally installed burglar alarm system that dials out (over a dedicated landline) to a monitoring station when an intrusion is detected. I'd like to modify it to send us an SMS (via the mobile phone network) and/or email (via wi-fi on a different landline) as well, just in case the phone line is cut, and to make sure we get notified immediately - the monitoring station tries to call on the landline first, then it calls our keyholders and the police, which all takes time. If I'm 5 minutes away and the alarm is triggered, I'd like to know straight away so I can rush home.
The alarm company have quoted a huge sum to make this change, because an updated control control panel would be needed to deal with the texting/emailing. I can't go cutting into their system or it will invalidate the maintenance contract, so I need to pick up when the alarm is triggered without any physical connection. Short of remotely detecting a current in the cable to the siren (a 12V DC signal, so how would I detect that?) it occurs to me that using Arduino to listen for the siren might be the best bet. But I'm an Arduino beginner and I have no idea whether it would be better/easier to detect a noise over a certain threshold - the siren is very loud, but the noise from the adjacent road can be pretty loud too - or to try and detect the particular sound frequency of the siren.
All suggestions gratefully received.