Immediately fall off to the right and attract the attention of a guided zap drone. As the second one comes down, jump and also lure the drone to the right side. When you enter the room on the left where the drones were, stand on that hump and jump to the diagonal space. Climb up the diagonal to emerge on the other side, where a chaingun drone looms. Through the rest of the level, dodge the drone's fire by constantly running, while still grabbing the switch. To be more cautious, you can wait for the chaingun to go around to the side opposite where your destination is.