Comments

That's funny. I noticed the correlation between population centers and "low click" numbers years ago, but always assumed it was for the benefit of the callers rather than the equipment.

A lot of your readers might not know what a http://en.wikipedia.org/wiki/Rotary_phone is.

Cororally: 911 is used because it is unlikely to be dialed by relay switching 'noise' that may occur during an electric storm (imagine 111, for example; false switches could occur during the dial time much more easily) . Other emergency numbers around the world, e.g., 999, 000, are used for the same reason. It'd be interesting to know if using 999 instead of 911 makes a noticable difference to the number of accidental 911 calls.

I worked in that industry for many years. The dial scheme was originally more complex than just the area codes. The original plan was NYX-NNX-XXXX where Y = {0,1}, N = {2 .. 9} and X = {0 .. 9}. Thus when the second digit was dialed, it was immediately apparent whether it was an area code (0 or 1) or an office code (never 0 or 1).
This was important if you were parsing the clicks, or tone sequence, as it happened. This was how the relay based "stepper" switched worked... each click moved your selector level.
Due to number shortages, the NNX became NXX, and later area codes became NXX also. The whole stepper process became unnecessary because computer-controlled switching became the norm. Who woulda thunk?

Oh, and Mr. Poisson originally developed his tables as an exercise he developed trying to determine what process he could use to kill his wife that would minimize his chances of being caught. He went ahead and poisoned her, and was caught anyway, or his science may have never been known.

@weshowe: Poisson = fish (in French)