telecom

AT&T Breakup-the day after in 1984

Telephony - Collection of items used in Communications

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Before modern electronic telephone switching systems came into use, dial tones were usually generated by electromechanical devices such as motor-generators or vibrators. In the United States, the standard "city" dial tone was a 600 Hz tone that was amplitude-modulated at 120 Hz.

Off-hook tone

Bell System Voices
Time Lady
Mary Moore
Jane Barbe
John Doyle

2600 Hz tone on a trunk

Look Mum No Computer Patrion