Oh shoot, sorry I didn't see the notification for this comment!
If you look at the maps on the wall, or in the Control Room, you'll see a blip that indicates where the exit is. If you go to the exit and open the door, you'll be automatically evacuated.
BUT, the blip will only appear AFTER you've survived until the timer runs out (shown on the Control Room interface). Just make sure you repair the transmissions when they go down, since the timer will pause until they've been repaired.
If a transmission needs to be repaired, you will hear a beep and be notified in the top left of your screen. You can find the broken transmission by going to the flashing red blip on the map.