SIP Trunk Configuration for 3CX

17 September 2014 | SIP Trunk telgo.SIP Connector

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Occasionally we receive screenshots and setup-Information from customers who have documented their PBX setup with the telgo.SIP Connector. We appreciate this feedback, and would like to share it with you. We hope it helps to speed up your setup. Obviously, this information (it is not advice) is provided “as is” without any representations or warranties, express or implied.


Today we are posting screenshots of a 3CX PBX with a telgo SIP Trunk. Thanks to Juergen S. for sending this in.


And here are the screenshots and our comments:




Make sure the country (country code) and the local area code are set according to your location and requirements. Please adjust – eg. Germany and 40 for Hamburg.

The standard format for number transmission with the telgo SIP Trunk is E.164 without leading zeros and without the plus sign (+). This applies to incoming and outgoing calls. telgo can provide and process different number formatting upon request. Please contact your Account Manager.



configuration-3CX_2STUN is not required and should NOT be used. telgo SIP Trunk has advanced mechanisms for NAT recognition and processing.
The public IP probably can (and should) be omitted. (Unverified writer’s opinion – comments please)




telgo SIP Trunk settings and Credentials/Password entry. Fill in accordingly.

Writer’s opinion: The “External Number” entry is probably not necessary. (comments/information are welcome)






The „CLIP no Screening“ feature (it’s a telgo SIP Trunk option –don’t forget to order it) allows the PBX to set the caller’s number when a call is forwarded to an external Phone. So when a call is forwarded to a mobile phone you’ll see the number of the caller (and not the PBX Number. To activate this option (it’s not shown in this screenshot) proceed as follows:

In the menu overview SIP field index:

  • Choose “FROM: User Part” in the drop down SIP field
  • Change the variable on the right to “OriginatorCallerID” Original Caller number will be sent
  • Choose Add/Update to activate the settings.







Codecs and their selection will be dealt with in a separate article.

Meanwhile here is the short version:

G.711 offers the widest compatibility and is not CPU-intensive (G.711a for Europe, G.711u in the USA)

telgo SIP Trunk also supports Wideband and HD Audio including G.722. Our favourite in this case.
G.729 offers compression and significant bandwidth savings. Voice quality is a little lower due to the loss incurred by compression.




The call rules allocate called numbers to a “route”. Usually, all numbers called will be sent to/via the telgo.SIP Connector as in the case above.
Please don’t forget to configure emergency numbers including their length. you see the configuration for Austria.



All the best for your install. We hope these screenshots are helpful for your configuration.


Don’t hesitate to send us any additional information or comments – and don’t forget the screenshots!


This is not a complete installation guide. It should help you to quickly get a working configuration for your 3CX PBX with a telgo SIP Trunk. Verify the integrity and security of your configuration before going live or connecting to any networks!



SIP Trunk Configuration for 3CX on September 17, 2014 rated 4.5 of 5