Doorbell needs plugging in when you get into the space. It's plugged in to a power strip along with some of the computers, which seem to sometimes power up by themselves, so the power strip gets unplugged at the end of the night.
A better solution is probably going to be to find a socket we can leave the doorbell permanently plugged in to. Maybe the same one and via a double-adapter, as there seemed to be limited positions in the space where the doorbell could be received.
Might need to also make a more prominent sign with details of the landline number on as a backup.