I used to own a tiny "alarm clock" that I would take on trips (though it was AA-battery powered). Nowadays, phones and even the cheapest wristwatches do the alarm clock job, it seems.The most likely 60Hz-required device is a simple plug-in clock, which syncs to the line frequency to keep time. Plug it in (through an adaptor) to a 50Hz line and it will run slow -- at 5/6 speed -- which is great if you want more sleep, but terrible if you are trying to catch a plane.