I think your system is 110 volt per line, I'm not sure quite how you use the other line to get 110 volts as well, I havent ever worked on your system. i suspect a phase inverter somewhere, but hey?
The UK system is now 220 volts. When I was a lad 50 years ago the UK had 240 volts and Europe had 220 volts. Once international travel became common there were many instances of european equipment being bought into the UK and soon after exploding all over the place. So to bring the UK into line with europe (and of course to save quite a bit of money) the UK dropped its standard voltage to 220. This is why you hear older english people referring to 240v.
To confuse matters a bit, all construction site tools in the UK MUST be 110 volt for safety reasons, so every contractor has to haul around really heavy transformers unless the site is big enough to have 110 volt distribution boards available
If you need more power than a trailing lead can supply, then you have to go to three phase, which gives you 410 volts through 3 live wires to the machine. But this is not allowed on construction site mobile tools.
In Europe, 3 phase is quite common in domestic premises as the power per phase available is fairly small. In the UK, 3 phase in a house is very rare.
It gets worse... USA uses 60 Hz power, europe and uk use 50Hz. This means that imported equipment (motors especially) run at different speeds than they are meant to, causing all sorts of reliability issues
Just to add a final spanner in the works, where I live now, in Cyprus, we still have 240 as standard, although if you use a test meter its usually 236v.
About 30 years ago in the UK I started work with a company that was importing American catering equipment (fast food stuff) and the first time I looked inside and found just a mass of black and white wires I thought someone was winding me up. It took quite a while and a lot of schematics study before I worked out how to install and repair them safely.
So, as I said at the start, It depends WHERE in the world you are, on what kind of electrical advice you can give and receive.