Newsgroups: rec.arts.theatre.stagecraft
Subject: Re: Clearcom interfacing with sound board
References: <[email protected]> <[email protected]>
[email protected] (Soundfreak03) writes:

> >I've got our sound board interfaced with our headset system for multiple
> >reasons, one of which being a shortage of headsets and beltpacks.  I've
> >got lines 3 and 1 going to both a mic in and an aux out, and everything
> >seems to work.  What we haven't tested, and I fear will be a problem, is
> >the ten to eleven volts the call signal places on the line.  Is this a
> >problem for either the output or the input?  How do I block the DC
> >signal?  Thanks for any help.
> 
> OK. To interface the system in just take it to an extra channel and CUT PIN 2.
> Pin 2 is the power for ClearCom. Pin 1 is ground and PIN 3 is the audio buss.
> Now ClearCom is line level so keep that in mind.  

This is true.

> So as long as you have PIN 2
> cut then there will be no voltage. 

This is not entirely true. The audio bus does not normally has 
any DC power on it, so it is prety near to 0V. 

But in case the call functionality is activated, a DC voltage of 
around 11-14V is applied to the audio bus. 

This kind of DC can be quite easily blocked with a capacitor. 

The mixing desk could have such capacitor already. 
But is batter to be safe than sorry.


-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/