Hybrid VoIP: Migration from conventional PBX to VoIP

Hybrid VoIP and SIP trunking -hybrid voip phone systemA hybrid VoIP system can bridge the gap between conventional PBX and VoIP telephony strategies in order to offer a more robust solution for organizations. These systems can facilitate the migration from PBX-based telephony to voice over IP.

There are two reasons the transition from PBX to VoIP has been taking such a long time: The first issue is the trust earned by an analog and time-division multiplexing (TDM) technologies over the years of use in business voice calls. In the early days of VoIP, people have raised issues regarding the suitability of internet-based VoIP in business environments. Of course, in those times, concerns about the quality of VoIP due to a lack of guaranteed bandwidth were legitimate.

On the other hand, PBX systems were highly reliable yet fairly complex and expensive to install. Regardless, companies used them since analog, and later, time-division based telephony was well established then. As a result, traditional PBXs lingered on in business environments even when other IT infrastructure was being replaced.

Nowadays, VoIP has become a norm in businesses after network upgrades addressed the majority of its call-quality issues. Consequently, the concept of unified communications as a service (UCaaS) emerged, and companies are able to afford advanced features without having to spend extensive capital.

This, in turn, enabled companies to use telephony and many messaging-related features without on-premise infrastructure. Moreover, the technology didn’t require ongoing maintenance needed by traditional PBX platforms.

Still, many companies have to come up with a plan to transition away from traditional telephony. Therefore, they might consider hybrid VoIP to get the best of both technologies at the same time.

What Is Hybrid VoIP?

Essentially, hybrid VoIP serves as a gap between traditional telephony and advanced VoIP methods. Therefore, it uses an analog or TDM system as its foundation and adds VoIP capability later.

For that, network engineers deploy Session Initiation Protocol (SIP) gateways to provide the interface for packet-based VoIP. Depending on which vendor you use for VoIP, you can leverage SIP gateway services for additional cloud-based functionality.

Since most traditional PBXs are built on proprietary hardware, hybrid components of VoIP may vary depending on each vendor. However, most hybrid components of VoIP use core SIP functionality as their VoIP standard.  Moreover, they provide connectivity to SIP endpoints.

After deploying hybrid VoIP over traditional PBXs, users can use existing handsets to make calls over IP. What makes this convenient is that they can now use VoIP technology in addition to any existing connectivity they had before thereby extending the life of the old system.

With that said, hybrid VoIP can also cut down the costs of traditional telephony without affecting the quality of your calls. The most common way to do that is with the help of SIP Trunking. SIP trunking allows you to use IP networks to establish a connection from a PBX to the Internet.

SIP trunking functions similar to how PRI lines work on a public switched telephone network (PSTN). However, this technique is designed for IP networks and is an alternative to PRI. In this scenario, SIP trunk routes voice calls over data networks instead of using analog lines or dedicated circuit-switched options. As a result, SIP Trunks replace the external PSTN connection to the phone systems with an IP connection with the help of a digital gateway which converts SIP calls into PRI signals used by PSTN. The use of digital VoIP gateways lets you connect conventional PBX to a VoIP provider via SIP protocol. The great thing about this solution is that it makes use of the existing PRI infrastructure and helps you use a hybrid communication system. By using SIP trunking in your organization, you can save as much as 30%-40% costs and enjoy the same voice quality you’re used to on PSTN networks.

Moreover, since SIP also supports the transmission of multimedia communications other than voice transfer, you can utilize the technology for the transmission of Unified Communications. Nevertheless, the use of SIP Trunking with the traditional PBX requires VoIP Gateways to enable PSTN to VoIP conversion.

Types of Gateways and How They Work

There are different types of VoIP gateways and they fall into two main categories, which are analog and digital.


A digital VoIP gateway is meant to connect a VoIP system to digital voice lines like E1, BRI, and T1. Furthermore, you can also use it to connect a traditional PBX system to an IP network.


An analog VoIP gateway is designed to connect a traditional analog phone to a VoIP phone. You can also use the system to connect a VoIP phone system to a PSTN. Since these gateways serve a dual purpose, they are available in two different forms, namely FXS and FXO.

FXS Gateway

An FXS gateway connects a traditional phone and fax machine to a VoIP system.

FXO Gateway

An FXO gateway connects a VoIP system to PSTN lines.

If you suspect that analog and digital gateways are being used for the same purpose, you are right. The only difference between both these gateways is the interface that each gateway uses to connect various solutions together.

To complete a soft migration, you have to connect the traditional PBX, along with IPBX and PSTN lines to the gateway. Here, too, you must consider the technology used on the PBX before using a certain gateway.

Can You Fit Hybrid VoIP into Your Telephony Strategy?

To determine whether hybrid VoIP can enhance your telephony strategy or not, you have to define your ultimate goal. If you are using an existing analog system, hybrid VoIP can supplement and enhance the system.

Moreover, it depends on which kind of additional features you want. For instance, a Unified Communication as a service (UCaaS) system offers a cloud-based platform with a plethora of additional features. However, it still doesn’t offer the same scope of telephony features that PBXs provide.

On the surface, it seems that both UCaaS platforms and traditional telephony have the same core features. For instance, UCaaS supports call transfers in call conversations. However, most people don’t know that there are different types of call transfer.

If businesses need special call transfer features, such as blind, intercom, mailbox, consultative, whisper, etc., hybrid VoIP can enable it.

Alternatively, if you only need basic telephony, then hybrid VoIP can pave your way to cloud-based UCaaS. By implementing hybrid VoIP, you can have a smooth migration from your existing PBX to a VoIP system. Adding VoIP will not only enable you to use a flexible system with additional features, but it will also help your company save costs.

Therefore, you can migrate to the cloud completely when you realize that the analog gear is not cost-efficient. Besides that, if you only have basic telephony needs, you can move directly to UcaaS and skip hybrid VoIP.

DLS Internet Services has been offering comprehensive UCaaS (Unified Communications as a Service) solutions since its inception in 1995. We strive to implement best practices in VoIP and deliver innovative business-to-business hosted PBX solutions. Our VoIP solutions employ SIP protocol and other VoIP technologies to ensure that customers have a seamless communication experience.

For further information on the company’s services, visit https://www.dls.net/.