Troubleshooting One-Way Audio
After answering an incoming call or placing an outbound call only one party is able to hear the other. The phone's screen indicates the phone call is established and is in progress, only audio from one party is present. This normally occurs on all outbound or inbound calls.
A few simple checks can point you in the right direction of the cause.
Check the phone where the issue is occurring:
- When placing or receiving a call ensure that the call is established. A good indicator of this is the call timer that appears on the screen.
- Verify that the handset is connected to the correct port on the phone. It's indicated by a picture of a handset.
- Try using the speakerphone to rule out the handset or the handset cord.
Network issues that usually cause this problem:
- Faulty NAT (Network Address Translation) or double NAT (Two routers both supplying NAT)
- Firewall Settings preventing RTP (voice) from traveling to the correct destination
- Network switching equipment or physical cabling issues
Correcting One-Way Audio
- Start by connecting the phone directly to the router or modem if possible or use the same connection and cabling as a working phone at your location.
- Make a test call to see if the issue still exists.
- Check with whomever services your network and internet connection such as your IT vendor or ISP to ensure that SPI (Statefull Packet Inspection), SIP Transformations, SIP/VoIP ALG (SIP Transformations), are all disabled and there are no other settings that may be the cause.
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