[sdiy] KN-75 optocoupler

[John L Marshall]

The neon optocoupler in answer machines is to detect the ring voltage. Talk 
voltage, at least in the USA, is -48 Volts, not enough to fire a neon lamp. 
Ring voltage is 90 Volts, typically 20 Hertz, enough to fire the neon lamp.

Take care,
John
www.sound-photo.com
www.antenna-farm.com

----- Original Message ----- 
From: "Paul Perry" <pfperry at melbpc.org.au>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Friday, December 21, 2007 4:47 AM
Subject: RE: [sdiy] KN-75 optocoupler


> If it is a LED/LDR opto, and you have 'tested' it by connecting a 9v 
> battery
> directly across the diode, then it is now just a LDR, the LED will have 
> been
> destroyed (no current limiting resistor).
>
> In Finnish, the KN-75 is called an "opto-putki" which I think is "light
> pipe" or "light tube" FWIW.
>
> As for neons in answering machines, I've seen them as static electricity
> discharge gaps.
>
> Paul Perry Melbourne Australia
>
>
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