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Title: Telephone ring detection
Author: Vincent Wong
Date: 29th March 2005
Below shows the oscilloscope signal for the telephone ring output from an opto-isolated circuit.
The circuit is setup such that when ringing happens (the line voltage will increase to 90V RMS), it will turn on
an opto-coupler LED. Any MCU can be used to count the number of pulses for each ringing signal and there the number of rings can be
determined.
The ringing output signal from opto-solated circuit
The output signal showing the ringing (too_toot...) tone
The ringing signal off time
The time between repetitive rings
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Copyright Notice: This article, including all text, documents and schematic diagrams, are the intellectual property
of Vincent Wong, and is Copyright (c) 2005. Reproduction or re-publication by any means whatsoever,
whether it is electrical & electronic, mechanical or electro-mechanical, is strictly prohibited under International Copyright laws.
The author (Vincent Wong) grants the reader the right to use this information for personal use only.
Commercial use is prohibited without express written authorisation from Vincent Wong.
Copyright of Vincent Wong. All Rights Reserved.
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