A little off but an answer to tggodfrey, we in Sweden actually had 220V now 230V but should at all circumstances be fully operational at 240V,
Translated with google translate from the Swedish Wikipedia this is what is says:
Voltage:
With voltage refers to the voltage that is normally found in a standard electrical outlet.
Voltage is sinusoidal and down with respect to the effective value and the frequency .
In Sweden voltage always an alternating voltage and the frequency is 50 Hz .
Sweden has three voltages: 230 V +6 / -10% 50 Hz. [1] [2] Standard voltage in any standard wall socket.
This is termed the phase voltage and the voltage between each of the three phases and the neutral conductor (and the earth wire )
at the distribution terminal to the incoming line.
Until 1988 this voltage was 220 V, and therefore, you hear sometimes that figure
to be mentioned in connection with the supply voltage, and some older appliances and outlets can also be labeled with 220 V.
They are nevertheless permitted for use at 230 V.
115 volts. Half the regular power supply, is permitted in wet areas.
Accomplished by means of an intermediate transformer that transforms the voltage by half to reduce the risk of injuries because
the risk of electric shock is greater in damp / wet environment. The same plug that fits in standard sockets in most cases.
Nevertheless, one should only use equipment suited to this tension in their application, such as some razors and curling irons.
Previously (before the increase in 1988) was the thrill of these outlets 110 V and some older appliances and outlets can also
be labeled so. These outlets have recently been increasingly replaced with sockets for standard voltage 230 V supplemented with RCD.
400 volts. This voltage is called the main voltage and the voltage between two phases of a three phase system.
They are phase shifted 120 degrees relative to each other. Until 1988 this voltage about 380 V, and therefore, you hear
sometimes that figure to be mentioned in connection with the supply voltage, and some older appliances and outlets can also
be labeled with 380 V. They are nevertheless permitted for use at 400 V. This voltage occurs only in three-phase power,
and in some permanently installed equipment, such as certain types of cookers, heaters and washing machines.
In most countries in Europe used voltages as above. In many other countries, including the United States and large parts of Asia,
the line voltage is 120 V, 60 Hz.
Heres also a list of the worlds all line voltages (in English non translated)
http://en.wikipedia.org/wiki/Mains_electricity_by_countryThe world is mixed soup of voltages and frequencies but most is so close together that they seldom give any problem, on the other hand
this is on the high voltage side of the transformer, on the low side that 10V or even 20V difference JAP/US will be transformed into a few millivolts,
with another word they will work just as good in the states as in japan, but if we were to put it in a european socket on the other hand.... =)
Fun thing is that half of Japan runs 50Hz and the other half 60Hz, so most original PC-Engine adapters says both... but the PCE doesn't care as the rectifier bridge and the capacitors (hopefully there is some capacitors or it will be pulsating direct current) will straighten that AC into DC.
Remember old cheap Gameboy adapters were they had very small or no capacitors and made the audio sound smattering and garbled.