Strain wad level 7

I can not get out of this level. I found the exit door but cannot get it to
open. There seems to be a switch by the door but it does not work. I got the
blue and yellow keys and cleared those areas. I cant find a red key door. I
did find the secret transport pad.
Any help is much appreciated.
Peace,OUT

p.s. What is the best newsgroup or chat for DOOM?