What Is Direct Inward Dialing (DID) & Do I Need It?

December 2, 2022 7 min read

Devin Pickell

Devin Pickell

How To Get a Business Phone Number

Need a direct phone number for your team member? Then you want a Direct Inward Dial number, known as a DID.

Instead of going through an automated phone menu or human receptionist every time, people can dial the Direct Inward Dial phone number to reach someone. It differs from a phone extension, which would also exist for users of a phone system.

In this article, we provide an in-depth look at Direct Inward Dialing, how it works, and its benefits to businesses today.

What Is Direct Inward Dialing?

Direct Inward Dialing (DID) is when a telephone service provider connects a block of telephone numbers to your company’s Private Branch Exchange (PBX). It allows businesses to set up virtual numbers that can bypass the main reception lines and go directly to a desk extension or group of extensions. DID can be used with local, premium-rate, or toll-free numbers.
Other common names for DID are direct-dial numbers, direct dial, and direct dial-ins. Essentially, when someone says, “reach me at my direct number,” this is what they’re referring to.
There is also an option for supporting a similar arrangement called Direct Outward Dialing (DOD). It is used for outbound calls from your office phone system. You would use DOD to bypass having to press a number before dialing or connecting to the operator.

What is a DID number?

From the perspective of a customer or client, a direct-dial number looks like any standard telephone number. However, DID is a virtual phone number that goes directly to an extension or location in your company. Think of it as a shortcut phone line.

These direct-dial phone numbers point inbound calls to an organization’s phone system. The function of relaying callers to an individual user makes that number “direct.” This dedicated call routing is managed by the VoIP phone system.

Unlike a landline (or POTS line), these numbers are directly routed through your company’s phone system.

How does a DID Work?

Traditionally, DID works in one of two ways: through Public Switched Telephone Network (PSTN) lines or Voice over Internet Protocol (VoIP). Let’s start with PSTN.

Direct Dialing on PSTN

First, a telephone service provider connects a set of trunk lines to the customer’s hosted PBX. Next, a provider allocates a block of phone numbers and assigns these to the customer as their direct-dial numbers.
When an inbound call reaches one of the direct-dial numbers, it is forwarded to the customer’s PBX via the trunk line. When the call arrives at the PBX, the dialed number and calling party are provided.
Finally, the PBX routes the incoming call directly to one of the business’ phone extensions without the need for an operator or an auto attendant.

How direct inward dialing works
Source: Cisco Certified Expert

In older phone systems, direct-dial functioned by using analog circuits. This meant that the customer’s equipment had to provide the low-voltage signaling for the phones in the system to work. The telephone company’s Central Office (CO) would check to determine if the line was operational and disable the circuit if it wasn’t terminating properly.
Typically, these analog lines relied extensively on the CO to provide signaling and call routing.
Trunks for DID service are unidirectional. So, it’s not unusual to combine the trunks with DOD. This means the direct-dial line can also call out and still be identified with the allocated DID phone number.
More recently, traditional phone services offer DID via Primary Rate Interface (PRI) circuits. These require you to have adequate trunk lines leased from the telephone company.
So, let’s say you are leasing eight trunk lines and have 50 DID phone numbers. If you have active calls on all eight of your trunk lines, when the ninth person calls a direct-dial number, they will get a busy signal. Alternatively, the ninth caller will need to be held in a separate queue.

Direct Inward Dialing on VoIP

VoIP is the most modern and flexible way to employ virtual direct-dial numbers with the help of SIP trunking. SIP makes the trunk line connections available as needed. These are not physical lines but virtual links across broadband only when you require them.

These virtual links are configured internally, and the numbers are linked to your extensions by a software application. You can do this yourself, or you can have your VoIP provider do it for you.

DID on VoIP is highly scalable. For example, if you decide you’d like to launch a sales campaign next month that requires you to have 20 new trunk lines, you can easily do it yourself. There’s no need to contact your telephone company, wait for them to allocate a block of numbers, and then send out a technician to physically connect the trunk lines to your business PBX.
In the past, you might’ve had to wait weeks to get this set up, and the cost would be substantial. Now you can configure it yourself.
VoIP systems have a variety of features that take time to learn. Thankfully, most VoIP providers offer professional onboarding and support. This goes beyond what traditional service providers can offer.

DIDs for faxing

The simplest way to use DID as a fax service is to connect your direct-dial line to a fax machine. Sounds simple, right? However, you’d be missing out on the more useful and powerful ways to route fax calls with DID.
A popular practice is to assign a block of direct-dial numbers to a computer that runs a fax server. This allows for multiple fax numbers for your company linked to a particular machine or even multiple devices.
Just like each team member within your company has an email address, you can assign them a fax number. When a fax comes in for a particular individual, it can be routed to the printer in their work area or even their computer and its printer.
Many DID fax servers also offer the ability to convert a fax to standard image files and then route this to the recipient’s computer or mobile phone. Employees don’t need to sit in the office waiting for fax anymore. Remote employees can receive their faxes without someone at the office routing them to them.

Do I Need Direct Inward Dialing?

You may have already invested in a reception system, but ask yourself, is it the most efficient way to handle your inbound calls?
There are times when you may want a prospect to skip the phone menu or receptionist and go directly to your sales department. What about separating where your enterprise versus small business customers are directed? If you have specific lines for customer service, sales, and other departments, chances are you could benefit from DID and setting up VoIP caller IDs — especially when paired with a top-rated VoIP provider.

Advantages of Direct Inward Dial Numbers

The benefits of DID apply to every business today, including:

  1. Cost savings: With DID, you can reduce the number of trunk lines required to connect your business. With a VoIP system, you can even forward the DIDs to different continents, saving long-distance costs.
  2. Time savings: Routing calls to the person directly, without the need for a receptionist or phone menu, saves time. Follow-up becomes easier for customers when their agent has a single number.
  3. Better customer experience: Customers can reach employees when they need them without hurdles. That can be a remarkable experience from the customer’s perspective.
  4. Team communication: Employees can contact team members via a dedicated extension, even if they are in different buildings, cities, or even countries.
  5. Local phone numbers: People prefer to call local phone numbers. A business operating in New York can set up a phone number in Miami or London for customers in that market.
  6. Existing equipment: With VoIP, direct-dial ins occur in the telephone network, and virtually, you won’t need to buy all new phones or hardware.
  7. Automated call forwarding: You can have your direct-dial line automatically forward incoming calls to your mobile phone or other temporary numbers without the customer knowing these private numbers.
  8. Flexibility: With DID, you have more control over where and when you receive calls. A mobile workforce demands a flexible solution. Combining the power of VoIP, DID, and SIP with mobile phones, email, and SMS equals a more robust telecommunications system for your business.
  9. Time settings: Automatically forward calls to different numbers at given times. This is great for after-hours support for different time zones, especially for global teams.
  10. Marketing attribution: By assigning different numbers to different marketing campaigns, you can accurately track the performance of each campaign.

Drawbacks of DID Phone Numbers

There are cases where a DID number may not be the right option for your business. For example, if you’ve experienced turnover recently and have direct-dial numbers assigned to former employees. Limited employee availability may also impact your decision to go with DID.

It’s up to your business to determine the importance of having customers, clients, and vendors reach departments directly.

  • High employee turnover: Customers may try to call a phone number not currently managed.
  • Employees aren’t available for calls: Incoming calls may disturb their ability to get work done.
  • Robocalls: A DID wouldn’t screen out incoming robocalls with an IVR or auto attendant.
  • Security: Employees with a publicly accessible phone number are targets for social engineering.

How Do I Get DID Number?

Give your customers and vendors a way to reach people and departments in your company with a Direct Inward Dialing phone number. DID allows inbound callers to skip the phone tree and bypass call queues.

The first step is to obtain one or more business phone numbers. It’s likely you already have some business phone numbers. You can transfer these through a method known as porting.
Next, you would assign these to each user in your phone system. This can be done from the administrative dashboard effortlessly.

A complete business phone system with Unified Communications - Nextiva

Adding the direct-dial features your team needs is simple when you go with an experienced VoIP provider, like Nextiva. We’ll help you determine how many direct-dial numbers you’ll need and what the most cost-effective solution for your business will be.

Once your DID service is set up, inbound callers will be able to reach your teams with low friction. In a world where great customer service is a competitive advantage, direct-dial numbers are just another way to provide personalized experiences.

Devin Pickell


Devin Pickell

Devin Pickell was a growth marketer at Nextiva. He combines his skills in content marketing, SEO, data analysis, and marketing strategy to meet audiences in their journey. He has helped scale SaaS brands like G2 and Sphere Software and contributed to G2's traffic growth. You can find him tweeting about e-commerce, sports, gaming, and business.

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