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How to detect ON/OFF Hook of connected

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nuttaphong191

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How to detect ON/OFF Hook of connected Line of Exchange side.
I want to detet ON/OFF hook status of line connected to exchange side
If I dial a number and picking the Handset of the called party, I should able to detech whether the Handset is picked or Not

Can any body help and if possible give the circuit

Thanks
 

_i386sx25_

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When off-hook, telephone set draws current from line. Line has a non-zero empedance. So to detect off-hook monitor the current at exchange side, monitor the line voltage at subscriber side. Easiest way to sense off-hook position put coil of a relay or optoisolator's input diode serial to line. When current passes through the coil/diode, relay/optoisolator out will short.

I would suggest reading the book "understanding telephone electronics" uploaded to forum numerous times.

https://www.edaboard.com/viewtopic.php?t=254530&highlight=understanding+telephone+electronics

https://www.edaboard.com/viewtopic.php?t=188161&highlight=understanding+telephone+electronics

https://www.edaboard.com/viewtopic.php?t=263869&highlight=understanding+telephone+electronics
 

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