Sadly Noel those "sound meters" are still in use! We to had a long mains lead where we would by pass the designated sockets!
The worst ones are where the sound is picked up by a mic at the back of the room but these also pick up background/audience noise too - so the more noise the audience makes the more the band has to to turn down!
One recent gig we took a couple of gagets with us that are used by PC companies that run their pcs even if the mains goes down. They do work and we still played on when the sound meter unit tripped out!


