Recently in Technical: Telephony Category
The scenario:
- You’re using Asterisk / FreePBX / Elastix / Trixbox
- You’re attaching to UK BT BRI (ISDN2e) lines
- Incoming BRI calls work
- Outgoing BRI calls don’t work
- When dialling using an outbound route you may hear, “All circuits are busy now” (Elastix you will)
You may see errors such as:
- Ext: 1 Cause: Unallocated (unassigned) number (1), class = Normal Event (0) ]
- “TRUNK Dial failed due to CHANUNAVAIL (hangupcause: 1) - failing through to other trunks”) in new stack
Potential Resolution:
Add to your dhadi-channels.conf the following for each span (we use Xorcom’s Astribank for BRI):
pridialplan=unknown
prilocaldialplan=unknown
Then just gracefully restart asterisk. To wait for an empty call volume, you can use this command in the asterisk terminal:
restart when convenient
Here are a few notes about BT ISDN 2e (BRI) lines that when I was first learning about phone systems configuration could really have done with being laid out. I hope it helps somebody in the UK (I’m assuming that this kit isn’t available in its exact form elsewhere).
- There are two types of ISDN line offered by BT: BRI and PRI (ISDN 30).
- BT’s ISDN 2e is BRI
- This is the same standard known as EuroISDN
- Each box on the wall supports two channels (lines)
- There are two RJ-45 connectors in the bottom of the present units. These exist so that you can plug two handsets directly into the box. (These are not standard PSTN handsets. The jacks are different - don’t try and force them!)
- Each RJ45 socket carries both lines i.e. you only need to plug in one of them for a PBX
- The type of cable required to fix in here is a standard Cat5 cable (or above).
