[Asterisk-Users] Calibrating both RX and TX gain?

[tmassey at obscorp.com]

asterisk-users-bounces at lists.digium.com wrote on 10/16/2005 07:49:38 AM:

> Here's a couple of ways to determine levels...
> 
> 1. using the model 4 transmission test set, attach the tone generator
> to one analog pstn line and the transmission level test jacks to a
> second pstn line. Dial from one line to other and measure the tone.
> Divide by two, and the result is the loss associated with a single
> analog pstn line from your location to your central office.

Remember, I'm not working with simple POTS lines.  I've got an Adtran TA 
612 providing CO lines from a T1.  There is nothing that says that the RX 
and TX settings on the Adtran are the same...  Therefore, just dividing by 
2 won't work.

Also, couldn't there be an issue on standard POTS lines where the effect 
upon a singnal between TX and RX is different?

It seems you're just exchanging one set of assumptions for another.  But 
you're the expert!  :)

> 2. use one of those analog pstn lines to dial the distant milliwatt
> generator (regardless of where its located), and measure the level
> of the tone.  Subtract the loss determined from step #1 and now you
> have the loss associated with facilities interconnecting your central
> office all the way to the distant milliwatt generator.

This doesn't address the problem above, correct?

> The end result will be whatever loss values you measure/calculate,
> you'll still have to play around with the rxgain & txgain to 
> minimize the echo while also maximizing the audio levels. The
> process will become a _qualitative_ eval process, not a quantitative
> one. It doesn't make any real difference which tools you use to get 
> there or exactly where the milliwatt generator happens to reside.

So how important or valuable will getting a milliwatt test number be?

Tim Massey
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