A DID number lets a customer dial straight through to the right person or team without going through reception. Your sales head, the accounts desk and the service queue can each have their own landline-style number, while all of them share the same phone lines and the same IP PBX. This guide explains what a DID number is, how Indian businesses get DID numbers, and how to route each one on your phone system.
What is a DID number?
DID stands for direct inward dialing. A DID number is a real phone number that your telecom operator delivers to your PBX over a SIP trunk or a PRI line. When someone dials it, the operator passes the dialled number along with the call, and the PBX uses that number to decide where the call should go.
The key point is that a DID is not a line. One SIP trunk or one PRI can carry calls for many DID numbers. You pay for the channels you need for simultaneous calls, and you can have far more numbers than channels.
DID number vs extension
The two are easy to confuse, because both are “numbers” on the phone system.
| Point | DID number | Extension |
|---|---|---|
| What it is | A public phone number from your operator | An internal number on your PBX |
| Who can dial it | Anyone, from any phone | Staff inside the phone system |
| Where it lives | On the operator’s network, delivered over a trunk | On the PBX only |
| Typical length | A full landline number with STD code | 3 or 4 digits |
| What it points to | Any destination on the PBX | One phone or softphone account |
A DID usually points to an extension, but it does not have to. It can just as easily point to a ring group, an IVR menu or a call centre queue.
How to get DID numbers in India
DID numbers come from licensed telecom operators, together with the trunk that carries them.
- On a SIP trunk: operators such as Airtel, Jio, Tata Communications, BSNL and Vodafone Idea offer SIP trunks with a series of DID numbers. Read our guide to SIP trunks in India for what to check before you sign.
- On a PRI line: a PRI E1 can also come with a DID series. Many offices moving from an old EPABX already have one and simply connect it to the new IP PBX.
- Toll-free numbers: a 1800 number reaches your PBX the same way, as a number delivered over a PRI or SIP trunk.
When you order, ask the operator how many numbers the series includes, how the dialled number will be presented to your PBX, and whether you can keep the series if you later move from PRI to SIP.
Routing DID numbers on Voxdial IP PBX
In Voxdial IP PBX, every DID is routed with an incoming route. Each route matches the dialled number and sends the call to a destination you choose:
- An extension: a direct line for a manager, doctor or account manager.
- A ring group: one number for a team, such as sales or the front desk.
- An IVR menu: the main number, with options for each department.
- A time condition: different handling in and out of office hours.
- Voicemail: for a number that only takes messages.
A route can also match the caller’s number, so a key partner calling your main number can take a different path. A route with no DID set becomes a catch-all for any number that does not match a specific route, which is a useful safety net.
Each route has its own settings for call recording, music on hold and a caller ID name prefix. The prefix adds a short label, such as “Sales” or “Ads”, in front of the caller’s name, so staff know which number the customer dialled before they answer.
DIDs for the call centre
If you run Voxdial Contact Center, the Inbound DID page maps each number either to one agent’s extension or to a call group, which is the queue your agents answer. This is how you publish a separate number for support, collections or appointments and have it land in the right queue. Read more on the contact centre page.
Showing your DID on outgoing calls
Direct numbers work best when they go both ways. Each extension in Voxdial has its own outbound caller ID, so when your accounts executive calls a customer, the customer sees the accounts DID and can call it straight back. Set this per extension, and check with your operator which numbers it allows you to present.
Practical ways to use DIDs
| Use | How to route it |
|---|---|
| Department numbers | Sales, accounts and support DIDs to their own ring groups |
| Direct lines for key staff | A DID to the person’s extension, with follow me to their mobile |
| Campaign tracking | A separate DID on each advert, with a caller ID prefix to tell them apart |
| Call centre queues | DIDs mapped to call groups in Voxdial Contact Center |
For people who are often away from their desk, pair the DID with ring groups and follow me so the call reaches them on their mobile.
Common mistakes
- Number format mismatch. The DID on the route must match exactly how the operator presents it. If calls fall to the catch-all route, check the format first.
- No catch-all route. Without one, a number the PBX does not recognise may be rejected.
- Destinations that do not exist yet. Create the extension, ring group or IVR first, then point the route at it.
BitVoice plans DID numbering and routing as part of every Voxdial IP PBX installation. Talk to our team about your numbers.
FAQs
What is a DID number?
A DID (direct inward dialing) number is a public phone number delivered to your PBX over a SIP trunk or PRI line, which the PBX routes to an extension, team, IVR or queue.
What is the difference between a DID and an extension?
A DID is a public number anyone can dial. An extension is an internal number on your PBX. A DID usually points to an extension, ring group, IVR or queue.
How many DID numbers can one SIP trunk carry?
One SIP trunk can carry many DID numbers. The number of channels limits simultaneous calls, not the number of DIDs. Ask your operator what series comes with the trunk.
Can staff show their direct number on outgoing calls?
Yes. In Voxdial IP PBX each extension has its own outbound caller ID, so customers see the person’s direct number and can call it back.
