My internet phone has one-way audio.
One-way audio commonly points to NAT/firewall or blocked RTP media, not Wi‑Fi speed alone. Test the ATA/phone by Ethernet and review SIP/NAT design.
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6 answers found · last checked 17 August 2026
One-way audio commonly points to NAT/firewall or blocked RTP media, not Wi‑Fi speed alone. Test the ATA/phone by Ethernet and review SIP/NAT design.
Packet loss, jitter, latency and upstream congestion cause broken voice. Test wired, pause uploads and capture a failing call time.
Check DHCP/IP, DNS, cabling, SIP credentials and whether double NAT, CGNAT or firewall/ALG behaviour changed.
Usually not unless the ONT/router/phone equipment has backup power. Ofcom requires providers to address emergency-call resilience, especially for at-risk customers.
Often, but compatibility depends on tone/ringing, connectors and the VoIP service. Alarms, fax, lifts and telecare need explicit compatibility testing.
Fax tones are sensitive to packet loss, jitter and codec conversion. T.38 support or an alternative digital document service may be required.