Indeed - but that was largely superseded when 'dual tariff'; meters came along, in which there was time-related switching between the two registers.In the distant past, we had two meters - the usual black peak one, plus a white off-peak one. From memory, the entire supply, was either connected to one meter, or the other - so it was down to us, to have our own system(s) to switch on/off at the correct times.
