Canceling a false alarm is relatively simple once you know how the system works. 
When your alarm is activated, a signal is sent to the Central Station by phone, radio or both. The operator at your Central Station then determines what the alarm is for and who to notify from their database.
If you have arranged to have them call your house before dispatching they will do so. If the call gets through and you give them the proper password, they will cancel the alarm.
If they don't call as is normal with fire and panic alarms or don't receive the proper password when they do, they will report your alarm to the police to be dispatched. Once the patrol arrives or the volunteers have been dispatched it will be too late to cancel a false alarm without penalty.
Your false alarm must be cancelled through your Central Station so we urge you to call them immediately when you know you have a false alarm. The Central Station maintains passwords to determine if your call is authentic. Having a "panic password" that sounds normal is a good idea in case anyone ever tries to force you to cancel an alarm. That is why the police will not cancel based on your call, we can't determine that you are not being forced to say that everything is fine.
Once you clear a false alarm with your Central Station they will either cancel the alarm or if it has already been dispatched, call back the police and request it be canceled. In the event the alarm was not yet dispatched to the volunteers (fire or medical alarms) or the police patrol has not yet arrived, upon verifying our own password with the Central Station, your false alarm will be canceled and you will not be subject to a false alarm fine