Configure the parameters for sending and receiving a fax over the VoIP channel. Two major approaches can be used for fax over IP.
- 711, sending fax signals in-band using the coding method used in regular voice transmissions, or
- 38, a protocol that sends fax image data over the IP network. T.38 is designed for more efficient and robust transmission compared to using the same method as voice communications.
There are pros and cons of both approaches described above. Consult your service provider for the appropriate configuration when needed.
Basic Setting
| Jitter Buffer Size | A jitter buffer temporarily stores arriving packets in order to minimize the impact of delay variations. If the jitter buffer size is too small, then an excessive number of fax packets may be discarded when network jitter occurs. If the jitter buffer size is too large, then it introduces additional delay. |
| Fax PTime | Packetization time for Fax packets. Available Options: 10, 20, 30, 40, 50, 60 (ms). |
T.38 Fax Support
| Enable | Enable/Disable the T.38 Fax feature. |
| Allow ECM | Enable Error Correction Mode (ECM) for fax transmission |
| Max Speed | Bit Rate. Choose a maximum fax transmission speed to be attempted: 2400, 4800, 9600, or 14400 bps. |
| Redundancy Level (Control) | Low Speed Redundancy. Number of redundant T.38 fax packets to be sent for the low speed V.21-based T.30 fax machine protocol. Default value is 2. Do not change the default value unless necessary. |
| Redundancy Level (Data) | High Speed Redundancy. Number of redundant T.38 fax packets to be sent for high-speed V.17, V.27ter and V.29 fax image data. Default value is 1. Do not change the default value unless necessary. |
