You need to delete the brown wall that is through the gap, between the two doors. To do this you need to use the barrel to extend your reach. Then you can go back to the Sender node, switch it to channel 4, and proceed to the next area.

Buddha, I've made it up to room 5 on your forgers cell map, but i'm completley STUCK!! could you show me how to do this one room i've tried for hours!