We had either headsets with long leads (sometimes plugged into the tug intercom system depending on where we were riding on the tug) or wireless headsets.. plus walkie talkies and hand signals as back up.
Comms were required between the people downstairs and upstairs in case there was an urgent issue, such as an APU fire during the tow.
Over the years I've done it both ways, using headsets and hand signals. Neither way is foolproof though - I was once being pushed back at AUH and the tug started pushing us the wrong way, I contacted the tug crew over the headset and informed them of their error - however as they didn't speak much English the only response I got was "Yes Boss" as we continued pushing in the wrong direction.
All I could do was apologise most profusely to the Tower ATC who were understandably quite p*ssed.
