115 volt

arriving at a standard

Concerns of electrocution held down the voltage of DC and AC services for domestic use, as it does today, arriving at an emerging standard of 220 to 240 volts. At the time of electrificaton in the United States, it was considered unsafe to go above 115 volts for domestic use. As it turned out, the high current required with 115 volts caused joints to overheat,

split phase

A split phase connection can grab some of the efficiency of a single phase 240 volt connection while still catering for 115 volt appliances at the load end, as well as catering for 240 volt appliances.

certain technologies alleviated disadvantage

incandescent globes, give a better function of globe life vs efficiency at a lower voltage. 20 watt fluros and live chassis solid state colour tv sets suit running off 115 volts.

Japan

Japan uses 100 volts, and their television manufacturing industry used to make tv sets that would use the mains via a simple linear voltage regulator (pre-a/v input) and generally added a transformer when they exported the tv set to a 220 / 240 volt country. This vintage of tv sets were thus very reliable. TV sets like the 1970s vintage NEC, were sold in Australia and Europe known as the now classic rank arena with a transformer that would also provide mains isolation.

With Japanese audio equipment they had a habit of using mains transformers lacking in voltage tappings.

Mexico

Mexico generally uses 115 volts, but there is known to be an area where 230 volts is used, but with the same American plug. Locals know of this detail This is probably the case where 220 or 240 volt appliances have a place to "find a home".

South Korea

South Korea used to use a 115 volt system, and converted to 220 volts during the course of the 1980s

Canada

Canada, although a British commonwealth country uses 115 volts, due to appliances transported across the border. Canada's wire and fittings etc are often rated to take 240 volts

universal power supplies

many computers and tv sets etc today are made with switched mode power supplies that can handle an input ranging from 100 volts to 240 volts AC. It may not be necessarily that obvious that a power supply from the united states can handle 240 volts, with the "240 volts" sometimes being in fine print. A Canadian or American tourist can often now be seen plugging their laptop into a power point (outlet) in Australia, without the nasty experience of blowing up their equipment. (needless to say that it is more than wise to read the fine print on your gear before plugging it in)

voltage multiplier power supplies

2 diodes and 2 capacitors can convert 115 volts AC to 315 volts DC, and this power supply can easily be converted for 240 volt use. The 2 extra diodes needed to form the bridge rectifier to handle 240 volts are generally on the circuit board and it is a matter of removing a certain link to make the power supply handle 240 volts. Electronic washing machines tend to have voltage multiplier type power supplies. These also have to have a link inserted to run off 115 volts or cut to run off 240 volts. (see computers for Cuba)