MLA Citation: Bloomfield, Louis A. "Question 816"
How Everything Works 20 Jul 2018. 20 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=816>.
816. How does a rotary phone switching system distinguish between the off-hook signal and the dialing signals, one through ten? - B
It doesn't. When you dial a rotary phone, it briefly hangs itself up one time for every number on the dial. Thus if you dial a "5", it hangs itself up briefly 5 times. In fact, you can dial the phone by tapping the switchhook briefly one time for every number. For example, if you want to dial a "5", tap the switchhook (hang up the phone) briefly 5 times very quickly. It takes some skill, but you can "dial" just fine without ever touching the dial. It used to be that people installed key locks on the rotary dial to prevent unauthorized use of the telephone. Unfortunately, this action didn't prevent someone with a nimble hand from dialing with the switchhook.

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