Sound in phone call is going one way or totally absent


Firewall settings

First of all, check your network firewall and other security settings. If some program is blocking ports 5060 or others used for phone interconnection, including RTP ports for voice interchange, system can experience voice loss or even can be unable to establish a call. All ports must be open. If you are using NAT or proxy tunneling, make sure ports are properly forwarded through NAT/proxy.

Codec settings

This can be caused by wrong codec settings of your PBX.

SmartPTT radioserver surrently accept only G.711 uLaw (PCMU) Codec. If your PBX supports codec prioritization, make sure that this codec is of the highest priority. Also, make sure that your PBX accepts G.711 uLaw as incoming codec. If it will not be set, voice from radio subscriber to phone user will not be delivered.

Routing table

Sometimes it can be caused by incorrect routing table setup.

To make sure that voice packets will be sent to correct destination, setup static route from your IP address to PBX's IP address:

- Press "Start" button, select "Run" option and type in "cmd". (In case of Windows 7, just type "cmd" right after pressing "Start" button)

- Press Enter

- Type  route -p add IP address of PBX mask IP address of radioserver

For example, if IP address of PBX is and IP address of radioserver is, then command will look like this:

route -p add mask

This command will create permanent static route to PBX using IP address utilized by radioserver. It will ensure that RTP packets will be delivered through correct interface and voice data will not be lost.

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