What Is Direct Inward Dialing (DID) & How Does It Work?

February 20, 2024 9 min read

Devin Pickell

Devin Pickell

What Is Direct Inward Dialing? Benefits, Examples, and How It Works

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

A DID allows callers to reach your employee directly without going through an automated attendant, receptionist, or call center. This differs from an internal phone extension, which only works for those calling from within your company’s phone system.

Using DID numbers for key team members boosts connectivity and efficiency as your business grows — whether you’re a small bsuiness building key customer relationships or enterprises strengthening existing relationships or keeping a professional image intact.

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 a phone system feature that allows external callers to dial directly to an internal extension without having to go through a switchboard or attendant. It assigns each user/extension in an organization a unique external phone number. So external callers can call specific people directly rather than through a receptionist.

To help you use DID, telephone service providers connect a block of telephone numbers to your company’s Private Branch Exchange (PBX) phone system.

With DIDs, businesses can set up virtual numbers that 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.

Direct inward dialing offers businesses convenience, customized call routing, and a more professional image.

What Is a DID Number?

From a customer’s or client’s perspective, 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.” The VoIP phone system manages this dedicated call routing.

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

How Direct Inward Dialing Works

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.

1. 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.

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.

2. 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.

SIP Trunking Diagram

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

3. 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.

How online faxing works

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.

Types of DIDs

The main advantage of DID is it allows direct external access to employees and departments over a single shared telephone line. Companies can allocate numbers based on their communication needs and workflows.

Here are some common types of DID numbers to choose from:

Types of Phone Numbers

Benefits of Using DIDs

DIDs offer plenty of benefits compared to traditional phone lines. The ability to dial employees directly is extremely useful for most modern businesses. Here are some notable benefits:

💰Cost and operational efficiencies

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.

VoIP helps direct-ins occur in the telephone network, and virtually, you won’t need to buy all new phones or hardware.

📱Better flexibility and mobility

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.

You can also automatically forward calls to different numbers at given times. This is great for after-hours support for different time zones, especially for global teams.

📈 Improved customer experience

Customers can reach employees when they need them without hurdles. That can be a remarkable experience from the customer’s perspective.

People typically prefer to call local phone numbers. A business operating in New York can easily set up a phone number in Miami or London for customers in that market.

By assigning different numbers to different marketing campaigns, you can accurately track the performance of each campaign, find areas for improvement, and enhance the customer experience even further.

✅ Productivity

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.

It also fosters better communication. Employees contact team members via a dedicated extension, even if they’re in different buildings, cities, or even countries.

You can even have your direct-dial line automatically forward incoming calls to your mobile phone or other temporary numbers without the customer knowing these private numbers.

Different Applications of DID

DIDs have many uses beyond basic business phone systems.

Examples of how businesses use DIDs:

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.

Here are some common limitations of DID and ways to mitigate them:

1. Limited call routing 

When using a basic DID, calls are directly routed to the assigned extension, offering limited control over call flow. This can be inefficient for managing high call volumes or directing callers to specific departments. Employ virtual receptionists, IVR menus, or call queuing for efficient call distribution.

2. Security concerns

DIDs can be vulnerable to unauthorized access if proper security measures are not in place. Safeguard DIDs with strong passwords, multi-factor authentication, and call masking.

3. Missing call insights

Basic DIDs often lack detailed call tracking features, making it difficult to analyze call data and optimize call handling. Choose providers with call tracking and integrate with your CRM for comprehensive data analysis.

4. High costs

Depending on the usage patterns and chosen features, DIDs can be more expensive compared to traditional phone lines. Negotiate volume discounts, utilize pay-as-you-go options, or explore alternative VoIP solutions.

How to Get DID Numbers

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.

Calling feature that customers love.

See how Nextiva integrates Direct Inward Dialing into your VoIP platform.

FAQs on Direct Inward Dialing

How much does a DID number cost?

There is no standard cost for a DID phone number. The price can vary depending on the telecommunications provider, number of DIDs required, and geographic location. Reach out to your VoIP provider to know more about the individual cost.

Do I need direct inward dialing?

Direct inward dialing (DID) allows callers to reach specific employees or departments directly without going through a receptionist or phone menu. Consider getting DID and setting up VoIP caller IDs if you have specific lines for customer service, sales, and other departments — especially when paired with a top-rated VoIP provider.

What is the difference between DID and call forwarding?

DID is a way to directly reach users through individually assigned numbers, while call forwarding redirects calls without changing the initially dialed number. DID provides direct inward access and call forwarding enables flexible rerouting.

What is the difference between DDI and DID?

DDI (Direct Dial Inward) routes external calls internally while DID assigns direct external numbers to internal extensions. Both allow external callers to reach users directly without an operator.

What is direct outward dialing (DOD)?

A similar arrangement called Direct Outward Dialing (DOD) is used for outbound calls from your office phone system. You would use DOD to bypass pressing a number before dialing or connecting to the operator when making external calls. Employees can dial outside numbers directly without going through a switchboard.

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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