i had my battery out my car for a day now my key fob wont work it ,its a cobra 7905 one and i cant find the instruction can anyone help.

It's a shot in the dark but my old Cobra required an extended press on the large unlock button. Something silly like 3 mins??

I am sure this is the alarm I had on my Impreza. Does it have a weird extra bit with your keys (looked like a small lighter with 2 metal contacts at one end?!). I was told that was used to reset the alarm/disable it if the fob was unavailable.