Are there gateway devices with both FXO and FXS ports?

Yes, some models of VoIP gateway do allow for both types of connections. This will allow you to connect your analog devices via the FXS ports and connect your VoIP devices to traditional PSTN connections.

Are there gateway models that support the T.38 codec for faxing?

Yes. The T.38 faxing codec is a protocol enabling users to send faxes over data networks.Though not available on all gateways, T.38 support lets VoIP users send faxes.

Are VoIP gateways only for connecting legacy phones to VoIP?

No, they are not. Years ago, VoIP gateways were used to connect the main offices to branch offices. For example, rather than make long-distance calls, businesses would use their VoIP connection to reach another office and then transfer the call to a PSTN. This way, calls made would be entirely local, despite originating hundreds or even thousands of miles away.

What is the type of wire needed to connect devices to a VoIP gateway?

Typically, both FXS and FXO ports use RJ11 wires to connect VoIP to the PSTN. This wire is the traditional phone wire that most of us grew up with.

What voice compression codecs are supported by most gateways?

As a rule, most gateways will support the standard codecs used to change voice into data packets. These include G.711, G.723, G.726, and G.729.

What is a VoIP Gateway and How Does it Work?

Written by Rebecca Drew

Written by

Rebecca Drew

UCaaS Researcher, Reporter

Rebecca Drew has been a part of the GetVoIP team for over five years. During that time, she has written on various business communication topics, from customer experience trends to business VoIP news to remote meeting tips.

Updated on November 16, 2023

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If you haven’t yet switched from a standard PSTN phone line to business VoIP, you should–the PSTN will be switched off in December 2025.

61% of businesses make the switch to cloud telephony (VoIP) at the end of their carrier contract.

Still, unless you plan to rely entirely on softphones, switching an existing legacy network to pure VoIP can be expensive. To avoid especially high costs, some businesses choose to use VoIP gateways to convert traditional telephone signals into VoIP data packets.

Overview
How it Works
Types
Benefits
FAQs

What is a VoIP Gateway?

A VoIP gateway is a hardware device that converts analog telephony traffic into digital data packets for transmission over the Internet.

These gateways also convert IP (digital) signals into analog signals, enabling two-way communication between a VoIP phone and analog phone. With a VoIP gateway, businesses can make/receive virtual VoIP calls on traditional desk phones without having to switch devices.

Because VoIP gateways make analog and digital signals compatible, businesses can keep their existing phone system hardware and infrastructure.

VoIP Gateway vs Analog Telephone Adapter (ATA)

A VoIP gateway differs from a VoIP box or ATA because while ATAs can convert only one phone at a time, some of the largest VoIP gateways can support up to 256 calls at a time.

A VoIP gateway, sometimes referred to as a media gateway, is a valuable tool for large offices ready to make the switch to business VoIP services, but want to continue to use their existing infrastructure to avoid the expensive or impractical switch to VoIP only.

How Gateways Work in VoIP

A VoIP gateway acts as a bridge enabling analog calls to be converted into digital packets (and vice versa.)

Here’s how it works:

Configure the VoIP gateway: The gateway is set up to connect all device ports, SIP trunks, and Direct Inward Dialing (DID) numbers to the gateway’s network IP.
Compression/Decompression: The VoIP gateway compresses digital signals from the PSTN into a series of ‘data packets’ for transmission across an IP network, while decompressing data packets originating from an IP network into a digital signal.
Signal Conversion: Digital signals are converted into an analog signal that can be sent across the PSTN.
Customize the Gateway: Finally, users create custom call routing rules to direct outbound calls across the PSTN. Information required to read backup data and restore the database should be stored on a device configuration file.

Types of VoIP Gateways

There are several types of VoIP gateways, each serving a different purpose:

Analog VoIP Gateways: Analog gateways connect to traditional landline phones (analog units are available for 2-24 lines)
Digital VoIP Gateways: Digital gateways enable users to connect digital lines such as BRI ISDN lines (Europe), PRI/E1 lines (Europe) or T1 lines (USA)
Hybrid VoIP Gateways: Hybrid VoIP gateways can convert analog and digital signals at the same time, enabling the concurrent use of Internet and traditional telephony networks
Session Border Controllers (SBC): SBC VoIP gateways use features like encryption and least cost routing to protect and control access to remotely hosted/cloud-based digital communications services (voice, video conferencing, text, chat)
Enterprise Session Border Controllers (E-SBC): E-SBCs are a type of session border controller typically installed at the edge of an enterprise or corporate IP network to route calls across a contact center environment

Benefits of Using VoIP Gateways

The benefits of using VoIP gateways include:

Phased Cloud Migration: With a VoIP gateway, businesses can keep existing hardware and stagger the cost of transitioning to cloud communications
Familiar Equipment: Using a VoIP gateway enables staff to retain their existing phones and devices, reducing training and setup times
Continue to utilize the PSTN network: VoIP gateways convert incoming PSTN lines to VoIP/SIP so that users can make and receive calls using the PSTN
Reduce costs: VoIP gateways let users make and receive calls via a cloud-based UCaaS system, drastically reducing costs by eliminating the need to purchase and maintain expensive hardware such as desk phones.