I agree that if you install an Alarm in YOUR house it can only be YOUR fault if it doesn't work properly.
If you supply and fit an Alarm in SOMEONE ELSEs house then it is your problem if it doesn't perform as you have supplied and fitted the alarm incorrectly.
If you supply and fit an Alarm in SOMEONE ELSEs house then it is your problem if it doesn't perform as you have supplied and fitted the alarm incorrectly.