Latency issues using PSTN trunks


hi all i have 2x UCM62xx set up one using SIP, the other using PSTN trunks.

the PSTN system is currently being trialed as our main system but since installing the system my boss has found that he often talks over clients when he receives a call. internal between extensions is fine no audio overlap/ latency. when we do get an external call you have to awkwardly have to wait 2sec before customer is finished saying what they need to say to avoid talking over their audio.

i can prove this by the fact the boss and i have tested the SIP and PSTN system simultaneously . the SIP system there is still latency but not so much as the PSTN trunks.

any ideas would be grateful as to how to shrink the latency til it is non existent


There are some tests to be done on the analog line to adjust the tones, impedance, etc. …
1 - press the “detect” button inside the “Analog Trunks” -> I recommend the semiautomatic
2 - Interface Settings/FXO Ports -> detect (obviously in Interface Settings all parameters must be corrected)

after each test restarts UCM, IF YOU DO ALL Correctly WHERE YOU HAVE AT LEAST OF THE BEST,
in case FX01 could be faulty/defective to use FXO2


hi i already have analog trunks configured for australian standard, how ever it is not just FX01 but also FX02 where there is this latency all i am after is a confirmation that there is more latency to be proved on using analog lines as opposed to SIP, the reason behind this is the company i work for deals with country to remote townships that use analog lines/PSTN, a sufficient explaination of how to reduce the wait of latency is what we are after. hope i have clarified a bit more.


did you do what I wrote on it?


There is apt to be somewhat more latency due the physical conversion of the line being analog and the rest of the system being SIP. How much, I am uncertain, and perhaps it varies based upon the line values as not all are created equal.

You should run the test as Damiano has suggested and if no improvement submit a ticket.


Did you ever find a solution to your latency problems? I am experiencing the same issues.