Hissing sound while making calls using freepbx pri line

Hi freepbx team

we are having issues with our freepbx as there is a lot of background hissing and disturbance while making outbound calls form our pri line any suggestions can help in fixing the issue

Usually that is an incorrect line coding or clocking setting between your PRI and the other end.

can you tell us how can we fix the inncorrect codding and clocking issue

The coding has to be the same as your providers, only one clock can be the master , usually the provider’s.

hi thanks for replying i am new to pbx feild can you elobarate it please

Maybe this will help:-


pay attention to the “Span Configuration” and if you are not in NANP land, also “Overiding PCM encoding”

can you check the link once 404 error has occurred while opening the page

I typo’d but corrected the link.

Hi @dicko Bro

so you mean to chan ge the span config and check

is the issue in dahdi"s system.conf

You need to check with your provider as to how the circuit is provisioned, then match it, if you use the dahdi helper module, then you will have to do it there as it overwrites system.conf, but when system.conf agrees with your provider that is “a good thing” the defaults for dahdi are based on NANP so you need to change the locale settings to suit your country, that should ensure that your calls go out ulaw ar alaw as appropriate add the

alaw=(your channels)

if the calls insist on using ulaw.