Relay & Radio Room
When you look in the door of the old tower you see an abandoned tube based radio in an equipment cabinet in front of you. Tower operators communicated with trains and probably marine traffic (for bridge openings) via this radio.
To the left are shelves which once contained relays, which were the logic of the Interlocking plant (switches and signals).
2011 photo. Compare to 2009 photo.
More photos here from the DB Tower & Bridge set.