Connect Andrews & Arnold SIP trunk to SessionPBX

Andrews & Arnold (A&A, also known as AAISP) is a UK provider of VoIP numbers. SessionPBX connects to an A&A number by registering to A&A with the number and its SIP password, the same way a desk phone would.

You bring your own A&A account and numbers. SessionPBX doesn’t supply A&A service.

About this guide. The A&A settings on this page were checked against A&A’s published documentation on 19 October 2026. The SessionPBX field names come from the Add SIP trunk wizard in the product. If A&A shows a different value in your account, use theirs.

Before you start

From the A&A Control Pages (control.aa.net.uk):

• Your A&A number, in international format, for example +441234567890
• A SIP password for that number. A&A doesn’t create one for you: open the number, select the Incoming tab, enter a password and select Apply.

A&A settings

Add the trunk in SessionPBX

1. Open the SessionPBX project and select Call Routing.
2. On SIP trunks, select Add trunk.
3. Provider: name the trunk, for example A&A +441234567890, and choose Generic carrier (registration).
4. Connection: set Host to voiceless.aa.net.uk, Port to 5060 and Transport to UDP. Leave Direction on Both directions.
5. Authentication: choose Username and password.
   • Username: your number in international format, including the +.
   • Password: the number’s SIP password.
   • Leave Auth realm and From domain blank. They default to the host.
   • Check that Register to this carrier is on. It’s on by default for Username and password. TLS registration isn’t available yet, so keep Transport on UDP.
   • Leave Registration user blank so it matches your number. SessionPBX registers with that number, and A&A sends your incoming calls back to it, which is how SessionPBX knows which number was called.
   • Leave Registration expiry at 3600 seconds.
6. Inbound: enter the same number under Inbound numbers, for example +441234567890.
7. Outbound: set Caller ID to your A&A number in international format. Leave Assert caller ID in on From header only.
8. Select Create trunk.

A&A’s Control Pages should show the number as registered within a minute or so.

More than one A&A number

Each A&A number has its own SIP password and registers on its own. Add one trunk per number, following the steps above.

So that outbound calls all leave through one number, leave Outbound number rules blank on your main trunk, and set Direction to Inbound only on the others.

SessionPBX addresses for A&A

Give A&A the address for the region your workspace is hosted in. If you’re not sure which region that is, email support@sessiontalk.co.uk.

SessionPBX accepts calls from carriers on UDP port 5060 or TLS port 5061. TCP isn’t accepted for incoming calls. Calls that SessionPBX sends to A&A can use UDP, TCP or TLS on whatever port A&A specifies.

A&A doesn’t need these addresses for a registered trunk, because SessionPBX connects out to A&A. Keep them in case A&A asks where your phone system is.

Route your numbers

On Call Routing, use Inbound number routing to choose where each number rings: everyone, a team member, a ring group, a call queue or a call flow. See Phone Numbers & Outbound Calls.

Allow members to call out

Outbound calling is off for new members. Open Team Members, edit the member, turn on Outbound PSTN under Access & features, and select Save member.

Members can dial numbers in international format, such as +447700900123. SessionPBX sends the number to A&A in international format.

Test the trunk

1. Call one of your A&A numbers from an outside phone and check that the right destination rings.
2. With Outbound PSTN on for one member, call a public number. Check that audio works both ways and that the called phone shows the caller ID you expect.
3. If you call into an IVR, check that key presses work. SessionPBX sends and receives key presses as RFC 2833 telephone events.

If calls fail, email support@sessiontalk.co.uk with the time of the call, the number you called from and the number you called.

Sources

• A&A: VoIP Phones – Generic Client 
• A&A: VoIP Handbook / Infopack (PDF) 
• A&A: VoIP information 
• A&A: VoIP Firewall