(newbie)--When we need echo cancellation feature on cards?

I’m new in this forum, also new to asterisk and IP-PBX.
Can someone tell me when we need echo cancellation feature on cards?
I need my E1 line to call a PSTN line, do I need echo cancellation? and
if I need from PSTN to PSTN connection do I need echo cancellation?
Is echo cancellation on sound card/headset not quite good enough?
I do really appriciate for some answer.

Thanks in advance


generaly it is a nuce feature to have as echo is realy anoing.
you need echo cancellation on the card to remove echo comming form the PSTN as analog phone lines can in some cases generate a lot of echo
especialy if the calibration is bad.
there is a number of ways that echo can acurre.

1 long analog PSTN lines (electric signal bouncing inside the cabel)
the longer the cabel the worse the problem

2 badly designed phones (most phons always play a littel of what you say in your headset so you can heare that you are talking, but some will also work the other way as what your heare is also transfreed to your mic, the speaker phone afect)

3 software bugs, (huu yes I know it but I have it often with my skype2skype that there is a 1-3 sec echo whre I’m talking with my self???)

Mark Petersen

Debian / Ubuntu fann

Thanks a lot