how to measure the impedance of PBX with A400P?

I want to set up and measure the impedance of the PABX so that I could calculate the echo return loss (ERL).

Has anybody done that before? what are the equipment needed and what is the testing circuit?


thanks a lot in advance.

Xing

hello:
you have to check the file in "fxo_modes.h" and your country,
and the code in wctdm.c
===================================
/* Set DC Termination:
Tip/Ring voltage adjust, minimum operational current, current limitation */
reg26 |= (fxo_modes[_opermode].dcv << 6);
reg26 |= (fxo_modes[_opermode].mini << 4);
reg26 |= (fxo_modes[_opermode].ilim << 1);
wctdm_setreg(wc, card, 26, reg26);

/* Set AC Impedence */
reg30 = (fxo_modes[_opermode].acim);
wctdm_setreg(wc, card, 30, reg30);
=====================================
you also need to check that with data sheet. i think it will tell your more details.
regards!
James.zhu

hi james,

my zone is 'SINGAPORE' and I can see from dmesg it's working under SINGAPORE mode, does it mean I don't have to change anything regarding to DC Termination / AC Impedance?

what does it mean with wctdm_setreg(wc, card, 30, reg30); ?

If I want to manually measure the AC impedance, what's the circuit setup?


thanks in advance,

Xing

hello:
I do not test the case you are asking. i think one possible way to test that is that, you make a dialplan, and make a incoming calls and outgoing calls. make sure the files are exactly same, you record the rx and tx file down to compare with the two files. you can check the method db_loss() in fxotune.c or run ./fxotune -i to see that. please check the more details:
www.voip-info.org/wiki/view/Asterisk+fxotune .
regards!
James.zhu