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

Do you 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 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 business building key customer relationships or an enterprise strengthening existing relationships or keeping a professional image intact.

This article provides 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 going 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,” they’re referring to this.

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

What Is a DID Number?

A direct-dial number looks like any standard telephone number from a customer’s or client’s perspective. 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 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 needing an operator or an auto attendant.

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 correctly.

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 trunks are not physical lines but virtual links across broadband only when required.

To connect a SIP trunk to your PBX for DID functionality, follow these steps:

1. Set up the SIP Trunk: First, get a SIP trunk service provider — Nextiva is among the best in the industry. This virtual connection is configured internally and linked to your extensions by a software application.
2. Configure the PBX: Once the SIP trunk is set up, configure your PBX to accept calls from it. When a call comes into your VoIP provider on any of your phone numbers, the call will be sent to your PBX over the SIP trunk.
3. Route the Calls: Finally, your PBX can route the call to an extension based on the number dialed. This ensures that incoming calls reach the correct destination within your organization.

You can do this configuration yourself or have your VoIP provider do it.

DID on VoIP is highly scalable. For example, if you decide to launch a sales campaign next month that requires 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 connect the trunk lines to your business PBX physically.

These virtual links are configured internally, and a software application links the numbers to your extensions. 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 to launch a sales campaign next month that requires 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 connect the trunk lines to your business PBX physically.

How Does DID Work with SIP Registration?

Direct Inward Dialing (DID) and SIP registration allow seamless integration between your traditional phone networks and VoIP systems. Here’s how it works:

When someone calls your DID number, the call is instantly forwarded to your SIP-registered endpoint. This endpoint could be a VoIP desk phone, a softphone on your computer, or even a mobile SIP app.

The main advantage is flexibility. You can receive calls directly on any SIP-compatible device, streamlining communication and enhancing connectivity.

Key Benefits

• Direct Connection: No intermediary—calls go straight to your specified SIP endpoint.
• Device Flexibility: Use desk phones, softphones, or mobile apps interchangeably.
• Efficient Routing: Enhanced call management for better responsiveness.

Integrate your communication strategy with DID and SIP registration to optimize how you handle inbound calls.

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.

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.

How Does DID Work with SIP Registration?

Direct Inward Dialing (DID) and SIP registration allow seamless integration between your traditional phone networks and VoIP systems. Here’s how it works:

When someone calls your DID number, the call is instantly forwarded to your SIP-registered endpoint. This endpoint could be a VoIP desk phone, a softphone on your computer, or even a mobile SIP app.

The main advantage is flexibility. You can receive calls directly on any SIP-compatible device, streamlining communication and enhancing connectivity.

Key Benefits

• Direct connection: No intermediary—calls go straight to your specified SIP endpoint.
• Device flexibility: Use desk phones, softphones, or mobile apps interchangeably.
• Efficient routing: Enhanced call management for better responsiveness.

Integrate your communication strategy with DID and SIP registration to optimize how you handle inbound calls.

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:

• Individual DID numbers: Each employee is assigned a unique external phone number that routes directly to them. This allows outside callers to reach specific employees without going through a switchboard.
• Department DID numbers: A whole department or workgroup shares a single DID number. The number rings a group of phones in that department so multiple people can easily handle calls.
• Location-based DID numbers: A specific DID number is assigned for each office location or branch of a company. Calls to that number ring phones at only that site.
• Toll-free DID numbers: Also known as toll-free phone numbers, external callers can reach employees/departments for free. The 800 number is routed to internal extensions.
• Virtual DID numbers: Numbers are not tied to a physical phone line but are hosted virtually. Calls are routed to whatever desk phones, softphones, or mobile phones the company specifies.
• Auto attendant DID numbers: Callers hear a menu of dialing options for different people/departments when calling this type of DID number, routing calls without a human operator.

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:

• Sales teams often use dedicated DIDs for lead-generation campaigns to track the performance of specific numbers and promotions.
• Customer service departments can set up DIDs for billing questions, tech support, or general inquiries and have calls routed more efficiently.
• Marketing teams use unique, temporary DIDs for certain advertising campaigns or events. Using a specific DID allows them to gauge response rates.
• Organizations with multiple locations can set up a DID for each location to allow seamless transfers between branches.
• Government agencies may use DIDs to direct calls to appropriate departments or personnel more efficiently.

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.

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.

FAQs on Direct Inward Dialing