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Old 4th Oct 2018, 9:13 am   #13
russell_w_b
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Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
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Default Re: British Telecom C2 klaxon and control box

Quote:
Originally Posted by Brigham View Post
How is it arranged to ignore every second ring?
The diode across the relay ensures that the back-emf maintains the relay on during alternate half-cycles of ringing current, and so doesn't chatter. I built a similar arrangement in lieu of a telephone bell for our works PAX once.

But if it's a relay with a heel-end slug on it, it'll be slow to release in any case and the further delay may cause it to miss the second ringing cadence.
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