rotary dialing

References

Images

On the left, a hand dials a number on a green rotary phone above a graph showing pulses (interruptions in DC current) that represent the phone being dialed. On the right, a hand presses a button on a red tone-dial phone above a representation of a push-button pad showing frequencies corresponding to each button.

rotary dialing: Media

telephones

Images

On the left, a hand dials a number on a green rotary phone above a graph showing pulses (interruptions in DC current) that represent the phone being dialed. On the right, a hand presses a button on a red tone-dial phone above a representation of a push-button pad showing frequencies corresponding to each button.

Two methods of call-number signaling in a telephone system

A major component of any telephone system is signaling. (Left) For telephones with...

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