SIP trunks can be used to connect to a large range of devices and services.
- Multiple trunks per domain. Each domain may have multiple trunks, inbound or outbound. Trunks may connect to local or remote gateways or register with SIP-compliant service providers.
- Flexible SIP headers. snom ONE SIP trunks allow a flexible configuration of the SIP headers, making it possible to deal with different interpretations of the SIP specification.
- CO-line emulation. CO-lines can be emulated in trunks, making it possible to give users the impression of a TDM-based system; for example, for shared-line appearances.
- Routing flexibility. Inbound calls can be routed based on extended regular expressions, giving administrators a great degree of flexibility for various scenarios. Outbound calls can be controlled with simple dial plan patterns.
- PIN code authentication. For certain trunks and users, the PBX may require entering a PIN code before using the trunk. This helps controlling cost for expensive outbound calls, while still allowing the feature from any extension.
- Telephone number representation. Numbers can be automatically converted into different formats, depending on country codes. Trunks can even have their own representation, for example for overseas calls.
- Global trunks. Global trunks can be shared between different domains. This is useful if there is only one trunk for multiple domains, for example a PSTN gateway.
- Security. Trunks can be marked as secure, even if they don't use SRTP encryption. This makes sense when you want to ensure that all calls are encrypted, but have a PSTN gateway which does not support encryption.
- Transcoding. Transcoding can be used to enforce selectable codecs on the trunk. Especially when terminating calls into the PSTN that helps reducing quality problems.
- Failover. When one trunk fails, the PBX can continue processing outbound calls on another trunk. That makes it possible to use multiple PSTN gateways in parallel or to have the PBX dial out on a local PSTN gateway when the Internet connection should not be available for service provider termination.
- DTMF detection. The PBX can be used to perform DTMF detection, in the event that the trunk provider is unable to do this.
- Pre-paid values. Trunks can be configured with rates that are used together with domain and account pre-paid values so that outbound calling is cut off once the pre-pay is used up.
- QoS. Each trunk estimates the quality of service using RTCP-XR and other methods, making it possible to estimate the user experience for the call.