the question of why the keyfob wasn't unsetting the alarm other than to come out with your oft repeated cheat tat comment..
Suggestion 1
One possible reason
If the user is holding down the button on the fob then its radio signal will be conflicting with the signal from the PIR sensor when the sensor is trying to tell the control panel it has detected movement. So neither the sensor nor the key fob can inform the control panel of the necessary information.
Querry 1
According to the manufacturer's they activate when the infra red image contains motion.
Are you perhaps confusing the 8 degrees with a rise of temperature in a hot spot heat detector as used in fire detection systems for detection of faults before they become a fire.
Hi Bernard. I have more respect for you so I will answer your suggestions and questions as follows.
Again from my head and without cutting and pasting.
Your first suggestion seems very unlikely. If what you are saying is true then the alarm would never function properly and would be easy to defeat.
I am sure that when a signal is sent to the panel it doesn't then overide any other input or that would cause so many problems. I am pretty sure that because of the way the system works in so many other ways that the reciever continually polls any devices it has registered on board. As such I presume that signal sending devices do not send a continual signal but short bursts. You can see when you set the alarm with a remote keypad for example that the send light flickers indicating the signal is probably sent in bursts. Thus allowing the contnually polling reciever to continue to pick up signals from other devices.
In relation to your question about the 8 degree differential. This does relate to pir operation.
The sensor calibrates itself to the heat image it 'sees'
ie the empty room.
Then when a heat source enters the room it identifies the intruder.
For the sensor to pick up this heat image against the background it has calibrated itself to then there has to be a differential between the temperature of the intruder and the precalibrated background of around 8 degrees centigrade.
This is not measured with a thermometer but it is just a rough guide as to the temperature difference that is needed for the sensor to notice a difference.
Hypothetically if you heated a room up to 39.6 degrees centigrade the sensor would then not pick up a person entering the room.
Since most rooms are around 22 degrees even with central heating then the heat signature from a body is easliy enough to trigger the alarm.
What would happen if an intruder came in dressed in foil to hide his escaping heat I don't know but it would be interesting.