XC4581 Linker Magnetic Switch for Arduino

I have a magnetic switch described as a "XC4581 Linker Magnetic Switch for Arduino". The best I can come up with as a data sheet is not very helpful. For example, I have no idea what Pin3 (NC) does :(

Can someone please point me to a functional datasheet.

Thanks

It's a simple reed switch activated when a magnet is within range, connect 5V to pin3 (Vcc), GND to pin4 and pin 1 to your input pin, pin 2 is NC (no connection). Here's a schematic ( for what it's worth :) ) https://s3.amazonaws.com/linksprite/LinkerKit/Magnetic+switch.pdf EDIT: These are often used for door and window switches with the switch embedded in the frame and an actuating magnet embedded in the door or window sash, (burgler alarm).

Plastic encapsulated reed switches are US$0.35 on ebay (shipped). Leo..

Thanks folks. (It was that 'NC' that had me puzzled :) )