Gamma SIP Trunk

Gamma is the UK’s leading SIP trunk provider. Gamma SIP Trunks connect cloud PBX and on-premises PBX systems directly to the Gamma network over an Internet connection, enabling call origination and termination on the public telephone network (PSTN).

Configuring a Gamma SIP trunk in PortSIP PBX is straightforward. Follow the steps below.

---

Step 1: Sign Up and Purchase Numbers

• Create an account with Gamma.

• Purchase your DID numbers from Gamma.

• Ensure your PortSIP PBX has a static public IP address, as Gamma uses IP-based authentication.

---

Step 2: Configure the Gamma Trunk in PortSIP PBX

1. Sign in to the PortSIP PBX Web Portal as System Administrator.

2. Navigate to Call Manager > Trunks.

3. Click Add and select IP Based Trunk.

Note Gamma SIP trunks are configured in PortSIP PBX as IP-Based Trunks (not Register-Based Trunks).

1. Complete the basic trunk settings according to the Configuring the SIP Trunk guide:

   • Trunk name (for example, Gamma-IP-Trunk)

   • Brand: Gamma

   • Hostname or IP address: Provided by Gamma

2. Save the trunk configuration.

The Gamma trunk appears in the trunk list with the status Online (expected for IP-Based Trunks).

---

Step 3: Set Up Inbound Rules

After the Gamma trunk is successfully added:

1. Navigate to Call Manager > Inbound Rules.

2. Click Add.

3. Select the Gamma IP-Based Trunk.

4. Enter the DID or DID range provided by Gamma.

5. Choose the destination (extension, ring group, queue, etc.).

6. Save the rule.

---

Step 4: Adjust Outbound Parameters (Required for Gamma)

Gamma requires specific SIP header formatting for outbound calls. You must adjust the Outbound Parameters of the trunk.

Steps

1. Navigate to Call Manager > Trunks.

2. Double-click the configured Gamma trunk.

3. Open the Outbound Parameters tab.

4. Configure the following fields:

Contact: User part Select OutboundCallerID (Outbound caller ID taken from the PortSIP Web Portal)

From: User part Select OutboundCallerID (Outbound caller ID taken from the PortSIP Web Portal)

P-Asserted-Identity: User part Select OutboundCallerID (Outbound caller ID taken from the PortSIP Web Portal)

P-Asserted-Identity: Host part Select TrunkHostPort (Trunk host and port)

1. Save the changes.

Important These settings are mandatory for Gamma to correctly identify and accept outbound calls.

---

Step 5: Set Up Outbound Caller ID (CLI)

Gamma requires the CLI (Outbound Caller ID) to be presented in E.164 format.

• The number must include a leading +

• Example (UK):

  [phone]

When configuring the Outbound Caller ID for an extension in PortSIP PBX, ensure the number is entered in this format.

---

Step 6: Create Outbound Rules

You can now configure outbound call routing:

1. Navigate to Call Manager > Outbound Rules.

2. Click Add.

3. Define the dialing conditions (number patterns, call type, etc.).

4. Select the Gamma trunk as the outbound route.

5. Save the rule.

For more details, please refer to Call Route Management.