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The Rotary Dial

Desk telephoneThe rotary dial was introduced for use with automatic switching equipment. The earliest dials had an eleventh finger hole labeled "Operator." This was added to reassure subscribers that they would not find themselves talking to the operator when they dialed a "0" as part of a telephone number. Dialing "Operator" sent the same signal as dialing "0." When people became used to dialing, this extra position was not necessary.

Desk telephone Child using rotary phoneWhen making a call, you use the finger hole corresponding to a digit to rotate the dial to the stopper. When the dial is released, it spins back to its resting position. As it spins, it makes and breaks the dialing circuit. The number of times it makes the circuit corresponds to the digit dialed: The farther the dial spins on the return, the more times it makes and breaks the circuit. The number of pulses sent from the dial operates a system of electromagnets in the switching system to make the connection for the number dialed. If you listen carefully when using a rotary telephone, you can hear the clicks as the circuit is made and broken behind the dial.

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