[TELECOM Digest Editor's Note: City of Chicago used DC power (rather
> than AC) -- at least in the downtown area -- until sometime around
> 1930. That's at least one reason why there were so many WUTCO clocks
> everywhere, instead of 'regular' wall clocks. Clocks cannot run on
> direct current; they require alternating current at 60 cycles.
I imagine the battery powering most wall clocks used nowadays would be surprised by that statement (if it could think, of course).
Clocks may have used the 60 hz cycle as a timing mechanism, of course, where a modern clock may use something else that oscillates, such as a quartz crystal.
Daryl
[TELECOM Digest Editor's Note: But you see, Daryl, in the little wall clocks with a battery in them, the battery does _not_ drive the escapement in the clock. The battery merely feeds a little motor which _winds up_ the spring which forces the escapement to work, which is how the old Western Union clocks operated as well. If you take the wall clock down from its place, hold it very quietly for a few minutes and listen, typically after every three or four -- maybe in some cases ten minutes, you'll hear a little 'whirring' sound which lasts for a couple seconds as the spring gets re-wound which in turn drives the escapement gear, causing it to repeatedly try to force its way past the two 'fingers' which alternatly jump up and down, trying to resist the pressure. You could as easily remove the battery totally then stand there and every five minutes or so use some tiny little tool to wind the spring by hand. In a _true_ electrical clock, where a motor inside spins continually there is no escapement; no reason to ever so slightly retard the gears. Putting it the other way around, if you removed the battery, then carefully lifed the 'fingers' and the pendulum out of the way, even with the battery gone, you'd see the hands on the clock spin around rapidly until such time as all the tension in the spring was gone. For true electric clocks, they require AC current at 60 cycles, or else they would speed up or slow down eratically as the current fluctuated. The old Western Union clocks would rewind their mainspring hourly; the little more modern clocks currently in use have _much_ smaller mainsprings and escape- ment wheels; the battery has to refresh them as stated above; between
3-5 minutes up to 10 minutes as needed. PAT]