[SML] Making a phone ring and it's handset speaker work on stage

[Jerry Durand]

A lot of PBX systems use 24V to get around safety standards (safety
extra low voltage), some even try using 12 but that's not good.

Phones were supposed to only detect AC and reject DC so that tapping
(pulse (rotary) dialing) didn't make the bell ring.  I found that
designing to that spec upset a lot of PBX makers.

(former chief rocket scientist at a company that made central office
test gear)

On 09/28/2016 10:36 AM, ken long via Stagecraft wrote:
> clear com is 24 volt dc if I remember right, phones were 48 volt talk
> dc and 90 volt ac for ring only ( frequency varied based on coil)
>

-- 
Jerry Durand, Durand Interstellar, Inc.
www.interstellar.com
tel: +1 408 356-3886
@DurandInterstel

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