Door Sensors


I have 9 doors that I want to put door sensors on. I will be using the Elk panel along with CQC to monitor the doors. What is the difference between open loop, closed loop and EOL sensors. Which will I need in order to tell if the door has been open, closed, etc.? What type is everyone using?
Open loop means the ELK input sees an open circuit when the door is closed and a short when the door is open. Closed loop means the ELK input sees a closed circuit, or short, when the door is closed and an open circuit when the door is open. EOL means the ELK input sees 2.2k ohms of resistance when the door is closed and either an open or infinite ohms or a short or zero ohms when the door is open. Depends on how you wire the type of switch and the resistor. I use EOL for 99% of my circuits.
Open and closed refer to the type of sensor that is on the door, EOL's are resistors that are used in conjunction with Open or closed sensors to help determin if there 1. is a damaged cable if you have problems with that zone, 2. if the cable gets cut or shorted during a burglery atempt.

I beleive that the type of sensor (open/closed) is up to you, just make sure your choice of alarm pannel accepts that type of sensor. (elk can use either)
I thought Normally Closed was the industry standard? If you use a Normally Open sensor and you have a wire cut then the panel will never know it. I would use a normally closed contact with an EOL if its a new install and how have an easy way to put them in. Or you can use the GRI contact with the EOL embedded in the contact.
Remember if using embedded EOL's in contacts to only use one contact that has an embedded EOL, otherwise the resistance of the zone loop will be too high.
with the open sensors I beleive the resistor is in parallel with the zone so there is always some resistance (or a short) on the zone input
I have three doors going into my storage building, can I daisey chain the door sensors? It doesnt matter which door is opened or broke into as long as it trips the sensor.