When it comes to CATI (Computer-Assisted Telephone Interviewing) surveys, one of the topics that raises the most questions is telephony. Most market researchers know it’s
possible to conduct telephone interviews directly from a computer, but it’s not always clear how this integration works or which technologies make it possible.

Questions such as “Do I still need a PBX?”, “What is a SIP trunk?”, “Why do some CATI platforms include a built-in phone while others require separate software?”, or “Can I use the VoIP phone system my company already has?” are far more common than you might expect.

The reason is simple: terms like PBX, SIP, SIP trunk, and softphone belong to the world of telecommunications, while market researchers are primarily focused on questionnaires, sampling, response rates, and data quality.

However, understanding these concepts is valuable even if you don’t have an IT background. It helps you evaluate CATI software more confidently, communicate more effectively with your IT team, and choose the telephony infrastructure that best fits your organization’s needs.

In this guide, we’ll explain the key concepts behind VoIP telephony, show how the different components work together, and explore how they’re used in a modern market research call center.

What is a VoIP?

Before discussing PBXs or SIP trunks, it’s important to understand one fundamental concept: today, most call centers rely on VoIP (Voice over Internet Protocol).

VoIP is a technology that transmits voice communications over a data network instead of traditional analog or ISDN telephone lines.

From the interviewer’s perspective, very little changes. They wear a headset connected to their computer, dial a phone number, and speak with the respondent just as they would
using a traditional desk phone.

Behind the scenes, however, the technology works very differently. Voice is converted into digital data packets that travel over the internet or a private business network, making
communications far more flexible and easier to manage.

For a CATI call center, this means agents can work from different locations, new workstations can be deployed quickly, telephony can be integrated directly with the survey software, and organizations can reduce their reliance on dedicated hardware.

Traditional telephony vs. VoIP: what’s the difference?

For many years, every call center workstation required a physical desk phone connected directly to the company’s PBX. Adding or modifying extensions often required assistance
from the IT department.

With VoIP, that has changed dramatically.

Today, the interviewer’s computer is the primary working tool. The phone is either a software application or a feature built directly into the CATI platform. Phone extensions can
be configured remotely, and the entire telephony infrastructure is generally easier to manage and scale.

This doesn’t mean the PBX has disappeared. On the contrary, it still plays a central role. The difference is that it’s now typically software rather than a dedicated hardware
appliance.

To understand how modern CATI telephony works, it’s important to become familiar with four key components: PBX, SIP account, SIP trunk and softphone.

CATI telephony glossary

What is a PBX?

PBX stands for Private Branch Exchange and is the technical term for a business phone system.

Its primary role is to manage all of an organization’s telephone communications. When an agent places a call, the PBX determines how that call should be routed. When an incoming call arrives, it decides which user or extension should receive it.

In addition to call routing, a PBX manages a wide range of telephony features, including:

  • Phone extensions
  • Call queues
  • Call transfers
  • User permissions
  • Call routing rules

In a CATI call center, the PBX serves as the core of the entire telephony infrastructure

Today, PBXs are almost always software-based. They can be deployed on-premises on a company’s own server or hosted in the cloud.

What is SIP?

One of the most commonly misunderstood terms in VoIP telephony is SIP, which stands for Session Initiation Protocol.

SIP is neither a software application nor a phone service. Instead, it’s the communication protocol that allows the different components of a VoIP system to communicate with one
another.

Using the SIP protocol, a softphone can register with the PBX, the PBX can establish and manage phone calls, and multiple devices can communicate using a shared industry
standard.

That’s why nearly every modern VoIP solution is advertised as SIP-compatible.

What is a SIP account?

A SIP account is similar to the phone extension assigned to a call center agent.

Each interviewer is typically provided with a unique set of credentials, including a username, password, and the address of the SIP server.

When the softphone starts, it uses these credentials to register with the PBX. Once registered, the system recognizes that the agent is available to place and receive calls.

What is a SIP trunk?

IlA SIP trunk is the connection between the PBX and the public telephone network.

Although it’s often one of the least intuitive concepts to understand, a simple analogy makes it easier.

Imagine the PBX as a train station. The SIP trunk is the railway line that connects that station to the rest of the national rail network.

In practice, the SIP trunk is typically provided by a VoIP or telecommunications provider and configured within the PBX. It carries both inbound and outbound calls to landline and
mobile numbers, with call charges generally billed according to the provider’s pricing plan.

What is a softphone?

A softphone is the software-based phone used by the interviewer.

Unlike a traditional desk phone, a softphone is simply a software application. It can be installed on a computer or, in more advanced CATI platforms like IdSurvey, integrated directly into the survey software interface.

From the user’s perspective, it offers the same core functions as a traditional phone:

  • Place calls
  • Answer calls
  • End calls

To operate, the softphone must register with the PBX using a SIP account.

How PBX, SIP trunks and softphones work together in a CATI platform

Once you understand the role of each component, it’s much easier to see how the entire system works.

Imagine an interviewer needs to call a respondent. The interviewer opens the CATI questionnaire and clicks to start the call. The softphone receives the call request and forwards it to the PBX. The PBX verifies that the user is authorized to place the call. It then routes the call through the SIP trunk to reach the public telephone network. Finally, the telephony provider delivers the call to the respondent’s phone number. The entire process takes only a few seconds and is completely transparent to the
interviewer.

In summary:

  • The CATI software manages the interview.
  • The softphone handles the voice conversation.
  • The PBX manages and routes telephone communications.
  • The SIP trunk connects the phone system to the public telephone network.

How this works in a CATI call center

In a modern market research call center, the goal is to minimize manual tasks and maximize efficiency.

Ideally, interviewers shouldn’t have to copy and paste phone numbers or constantly switch between different applications.

When CATI software is integrated with the phone system, the workflow becomes much more streamlined:

  • The interviewer opens the questionnaire.
  • The respondent’s contact information is displayed.
  • The interviewer starts the call directly from the questionnaire by clicking the phone number.
  • The interview is conducted.
  • Responses are recorded.
  • The system automatically moves to the next respondent.

Reducing the number of manual steps doesn’t just improve productivity. It also minimizes the risk of errors, creates a better experience for interviewers, and makes onboarding and training new agents much easier.

External vs. built-in softphones

Not all CATI platforms follow the same architecture.

Many solutions simply control a separate softphone installed on the user’s computer, provided that it supports the protocol used by the software—typically SIP.

In this setup, interviewers work with two separate applications: one for managing the questionnaire and another for handling phone calls.

This approach offers several advantages, particularly for organizations that already have an established VoIP infrastructure.

However, there’s another option.

Some CATI platforms include a softphone directly within their interface. For interviewers, telephony becomes a seamless part of the interviewing process. All essential calling functions are available within the same screen, eliminating the need to switch constantly between applications.

From a technical perspective, however, nothing changes. A PBX is still required, and the system still relies on a SIP trunk.

The only difference is the user experience.Cambia semplicemente l’esperienza dell’utilizzatore.

Can you use an existing PBX?

This is probably one of the most frequently asked questions—and in most cases, the answer is yes.

If your organization’s PBX supports the SIP protocol, it can often be integrated with CATI software without requiring significant changes to your existing telephony infrastructure.

This is particularly valuable for research organizations that share their phone system with other departments or have already invested in a VoIP platform.

Other organizations prefer to dedicate a separate PBX exclusively to CATI operations, keeping the call center’s telephony independent from administrative or sales communications.

There isn’t a single solution that’s right for every organization. The best approach depends on factors such as organizational structure, the number of interviewers, IT policies, and
operational requirements.

From a telephony perspective, every organization has different needs. Some prefer to leverage their existing VoIP phone system, while others want a fully integrated solution
that requires minimal configuration.

For this reason, professional survey software such as IdSurvey typically supports both deployment models.

This flexibility allows the platform to adapt to a wide range of organizations—from small market research firms to large-scale call centers with dozens or even hundreds of
interviewing stations.

VoIP calling from CATI software – FAQ

Can a softphone work without a PBX?

In a professional telephony environment, typically no. A softphone must register with a PBX – or an equivalent cloud-based telephony service – to properly place, receive, and manage phone calls.

Does a SIP trunk replace a PBX?

No. A SIP trunk connects the PBX to the public telephone network, but it does not perform the call management functions of a PBX, such as routing calls, managing extensions, or handling call queues.

Can I use my existing PBX with CATI software?

In most cases, yes. If your PBX supports the SIP protocol, it can usually be integrated with CATI software. However, you should verify the integration methods supported by your specific CATI platform.

Do I need a physical desk phone?

No. Today, many call centers operate entirely with USB headsets and softphones running on a computer or built directly into the CATI platform.

What’s the difference between VoIP and SIP?

VoIP (Voice over Internet Protocol) is the technology that enables voice communications over a data network. SIP (Session Initiation Protocol) is one of the protocols used to establish, manage and terminate those communications.

Does CATI software need to include a built-in PBX?

Not necessarily. Some CATI platforms integrate with an organization’s existing PBX, while others include a built-in PBX or are designed to work with a dedicated telephony solution. The right choice depends on your organization’s existing infrastructure and operational requirements.