You’ve got it right, in a nutshell Martin. There are only two rates commonly called a Day rate and a Night rate. An E7 meter records just two periods per day (Day and Night) and an E10 meter records 3 Day rates and 3 Night rates per day – in my case Night rates are 00:00 hrs – 05:00 hrs, 13:00 hrs – 16 hrs and 20:00 hrs – 22:00 hrs (total 10 hours) with the appropriate day rates between those hours. It’s the meter that does all the switching as it’s pre-programmed, usually hard wired and it indicates which mode it’s in by displaying the reading and the reading number (e.g. 1=Day rate, 2=Night Rate). I live in a block of flats and we have 34 E10 meters in the utility room but they don’t all switch say at 13:00 hrs for the afternoon cheap rate. Rather the switch over times are staggered to avoid electricity surges at the switch over time. This is achieved by deliberately making each meter clock slightly fast or slow, e.g. mine actually switches on to the afternoon rate at 13:22 actual time i.e. my meter clock is 22 minutes slow. Bear this in mind when trying to set central heating or hot water timers to use the cheap or night rate electricity.