AVR Freaks

I assume motor speeds are related by a factor of 2. Ie in Australia with 50Hz. mains we would have 750 & 1500 (ignoring slip) with 4 & 2 poles respectively.

Actually, multi-speed induction motors are usually much stranger. The lower speeds are usually small reductions from the "full speed". Tricks are played with the windings but not by factors of two. A 3-speed blower motor may go from 1000 to 1380 rpm, for example.

The center tap on the secondary on the 'pole pig' transformer is the earth ground.

Usually in neighborhoods, each transformer will serve more than one house. A "pole peg", depending on its size, might only supply two to four. With underground utilities it seems larger transformers are used which serve a larger cluster of houses. Out in the country you might have your very own. In the US, 240v usually powers your electric oven, range, electric clothes dryer, air conditioning equipment and if you have them, electric water heater or electric comfort heating. The 120v wall outlets, lighting fixtures and smaller appliances are divided approximately evenly between the two 120v legs to evenly load the transformer secondary. The neighborhood transformers are ultimately fed from high voltage three phase, but sometimes an entire street will be fed from one three phase leg, or, all three phases may run down the street and smaller numbers of transformers might be fed from each phase.

Thanks Bob,
So you also have two different wall sockets in your homes. One for single phase & one for two phase. I guess you must have the odd person who connects 220V to 110 V equipment!
I reckon the US should upgrade to metrics & 240V mains. The rest of the world has.