Door sensor question

I have a 4 core wire going to a door sensor in my dining room, to get there it passes by the kitchen.

What I would like to do is fit a door sensor to the rear door of the kitchen.

Am I able to split off the existing wire that goes to the lounge or not?

I'm not 100% sure if i would work, as one magnet would be open and the other one closed (assuming the crooks didnt break into both doors at exactly the same time )

Just looking for a bit of clarification.

In an ideal world i would run a new cable, however it would prove extremely difficult.

Each sensor should be connected to it's own zone. Assuming you have 2 zones available then you need a pair of wires for each door.

If you only have one zone then the door contacts will need to be in series. The contacts are closed when the doors are shut and either door will trigger an alarm. If necessary you can make the series connection at the control box if the wiring is difficult.

If they can be wired in series I will do that.

I upgraded the alarm when I moved into this house, however re-used some of the existing cables that were tricky to replace. I used 8 core, the older stuff is only 4 core which is whats causing the problems for me.

Best of luck. I always check out the sensors before wiring to the control box. A meter with an electronic buzzer or a ohm meter will tell you if the contacts are working correctly eg when either door is opened indication at the control panel end says Open. If you don't have a meter try to borrow one. Do not use a lamp as the current could damage the reed switch in the door unit.