I have a security system that only suppports a rj45 jack for internet. The building I'm in has wifi but no cables or jacks for rj45 nearby. Is there an adapter for wifi to cat5/rj45. I need it to work like the reverse of a router. I don't want to waste money to find out, but I've seen a rj45 to usb adapter before. If I get a wifi usb card plug it in to the adapter and then to the back of the security sys. will that work or doesn't the usb wifi card need computer software to work? Why can't they just make an "instajack" for cat5/rj45 cables instead of for phone line???