asterisk users - Sep 2004 - Effectively using a telco Type 102 Milliwatt Test line with ztmon itor -v to set txgain/rxgain in zapata?

I am trying to obtain optimum gain settings for a bank of analog lines
connected to a channel bank. My telco has provided a 'Type 102' test
line to
use for incoming level calibration. This is functionally equivalent to app
Milliwatt(), but provides tone from the CO inwards.

Question is, how should one use this a 0dbm test source with ztmonitor? Am I
correct in understanding that a 0dbm level should provide a 100% drive in
the level monitor, not a 50% drive as is otherwise 'optimum' for regular
voice traffic? 

Kris Boutilier
Information Systems Coordinator
Sunshine Coast Regional District

> I am trying to obtain optimum gain settings for a bank of analog lines
> connected to a channel bank. My telco has provided a 'Type 102'
test line to
> use for incoming level calibration. This is functionally equivalent to app
> Milliwatt(), but provides tone from the CO inwards.
> 
> Question is, how should one use this a 0dbm test source with ztmonitor? Am
I
> correct in understanding that a 0dbm level should provide a 100% drive in
> the level monitor, not a 50% drive as is otherwise 'optimum' for
regular
> voice traffic? 
The ztmonitor app is a relative indicator and is not actually calibrated
to anything.

If your play in the telephony marketspace, then purchase a transmission
test set that can display levels, etc. They are made by several different
companies and range in price from about $300 for a simple analog test
set (looks almost like a voltmeter), to well over $3k for fancy ones that
have dsl test modes, etc. Triplett (www.triplett.com) makes several 
different models of which the model 4 & 5 have a tone generator that
can be somewhat useful as well. Lots of other sources for the same.

> I am trying to obtain optimum gain settings for a bank of analog lines
> connected to a channel bank. My telco has provided a 'Type 102'
test line
to
> use for incoming level calibration. This is functionally equivalent to app
> Milliwatt(), but provides tone from the CO inwards.
> 
> Question is, how should one use this a 0dbm test source with ztmonitor? Am
I
> correct in understanding that a 0dbm level should provide a 100% drive in
> the level monitor, not a 50% drive as is otherwise 'optimum' for
regular
> voice traffic? 
Yes, that is correct.  the 0dbm level should provide 100% drive in the level
monitor.  Actually, I found it to be more than 100%. The grahical display
was at 100% but the quantative reading only read about 6000.  I needed to
add a couple db to the rx gain to get it to around 14500.  It you are
running Asterisk v1.0.9 you only need to edit one line in your
usr/src/zaptel/ztmonitor.c file and then recompile the zaptel driver.
 
Change line 261
 
fprintf(stderr, "Usage: ztmonitor <channel num> [-v] [-f
FILE]\n");

 
to
 
fprintf(stderr, "Usage: ztmonitor <channel num> [-v | -f
FILE]\n");
 
Recompile
 
cd /usr/src/zaptel
make && make install
 
Run ztmonitor in verbose mode
 
/ztmonitor 1 -vv
and you should see RX and TX levels in number form on the right hand side
 
 


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