# SIP Domain

*Opentact users enjoy the flexibility of creating multiple SIP domains effortlessly through the Opentact Portal. An example of a SIP domain is `sip://acme.opentact.org`. Within each SIP domain, users can define and manage numerous SIP users, each connecting to the SIP domain through SIP Registration.*

*Once a SIP device successfully registers with your SIP domain, various functionalities become accessible:*

1. **Inter-SIP Device Calls:**
   * Seamlessly initiate calls from one SIP device to another within the same SIP domain.
2. **PSTN Network Calls:**
   * Place calls from SIP devices to the Public Switched Telephone Network (PSTN) if the SIP domain is associated with an Outbound SIP Domain.
3. **Inbound Calls for Your Phone Number:**
   * Facilitate the reception of inbound calls for your associated Phone Number by employing a SIP Control APP. This application efficiently forwards inbound calls to a designated SIP User, such as `sipuser@your_domain.opentact.org`.

*Opentact empowers users with versatile communication capabilities, ensuring effective management and utilization of SIP domains for seamless connectivity.*


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