Japan has two separate electrical grids that operate at different frequencies: 60 Hz in western Japan and 50 Hz in the east. Shinkansen bullet trains run on electricity, but is it 50 Hz or 60 Hz? And what happens when a train crosses over the frequency frontier?
The Tohoku Shinkansen runs on 50 Hz. The Sanyo Shinkansen, which runs from Osaka to Fukuoka, goes on 60 Hz. But the Tokaido Shinkansen travels through both eastern and western Japan. So does the more recent Nagano Shinkansen. So how do they do it?
On the Tokaido line, the bullet trains run on 60 Hz, drawing from converting stations when they go through 50 Hz territory in the east. On the Nagano Shinkansen line, which is more recent, the trains are equipped with on-board converters. They draw 50 Hz electricity from Tokyo to Karuizawa, then 60 Hz from Nagano on.
Alice Gordenker アリス・ゴーデンカー 
Love your blog.
Re: 50 /60 hz, frequently referenced as a perfect case study in early non-tariff trade barriers; Japanese consumer electronics manufacturers must meet both standards, and therefore can sell anywhere in the world. The cost to Japanese citizens is irrelevant.