What is a VoIP Gateway?

A VoIP gateway allows you to convert between a traditional telephony connection and a modern VoIP connection using SIP.

There are two types of gateways: digital and analog.

  1. Digital gateways convert voice media between digital TDM connections and VoIP connections.
  2. Analog gateways convert voice media between FXO and FXS connections and VoIP connections.

Conversions can go from SIP to traditional, traditional to SIP or even SIP to SIP for the purposes of failover or transcoding. In a traditional network to SIP deployment, a gateway significantly reduces operating costs by connecting a legacy business phone system with dynamic SIP trunking services. SIP to traditional network deployments use a gateway to connect a modern SIP communications system with digital or analog service from legacy carriers. There are many applications for VoIP media gateways.

Photo of Digium D80 IP phone and Digium analog gateway

VoIP Gateway Diagram: VoIP to PSTN

Public Switched Telephone Network T1/E1/PRI to VoIP

A VoIP gateway can connect a modern VoIP-only system, for example a virtualized IP PBX, to a PSTN PRI trunk.

VoIP Gateway Diagram: Analog to VoIP

Public Switched Telephone Network Analog to VoIP

A VoIP gateway can connect a modern VoIP-only system to analog telephone lines, analog telephones, and fax machines via FXO/FXS ports.

VoIP Gateway Diagram: SIP to ITSP

VoIP Provider to Legacy PBX

An IP Media Gateway can be used to upgrade a legacy business phone system allowing it to use a SIP trunk out to an ITSP. SIP Trunks are more cost-effective than expensive legacy T1 lines.

VoIP Gateway Diagram: Legacy PBX to IP PBX

Legacy PBX to IP PBX Migration

The SIP gateway also acts as a bridge connecting a legacy PBX via a PRI interface and an IP PBX via a SIP connection to support a migration initiative.

VoIP Gateway Terms / Acronyms:

  • VoIP - Voice over IP

  • SIP - Session Initiation Protocol

  • IP - Internet Protocol

  • TDM - Time Division Multiplexing

  • PRI - Primary Rate Interface

  • ISDN - Integrated Services Digital Network

  • PSTN - Public Switched Telephone Network

  • ITSP - Internet Telephony Service Provider

  • FXO - Foreign Exchange Office

  • FXS - Foreign Exchange Subscriber

Other Names for a VoIP Gateway:

  • IP Media gateway

  • SIP gateway

  • Voice gateway

  • TDM gateway

  • PSTN gateway

  • PRI gateway

  • ISDN gateway

  • Digital Telephony gateway

  • Analog gateway

Test Drive the Best GUI for VoIP Gateways

Want to know how easy it is to set up a Digium gateway? Log in to our demo system and take it for a spin! Digium's award-winning GUI is known for its intuitive design and attractive visual appeal. Everything is easy to manage so you are up and running in minutes. Other gateways are complex and difficult to configure. They cram in unnecessary features, driving up the cost and cluttering the interface. Digium VoIP Gateways keep it simple so you get high performance for SIP conversion and more time to focus on what's important.

Digium D80 and Analog Switchvox G080 Gateway

Seamless Integration with Switchvox

Digium’s VoIP gateways are designed to seamlessly integrate with the award-winning Switchvox Unified Communications system. Switchvox customers can enjoy guaranteed platform interoperability and quick configuration during deployment. With features such as automatic discovery and call routing, system setup can be accomplished in a matter of minutes.

VoIP Gateways for Switchvox

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Digium G-Series Appliances

G080 Series VoIP Gateway

G080 Series

Digium’s G080 Series VoIP Gateways are 8-port analog gateways available in 3 separate configurations: 8 FXO ports, 8 FXS ports, & 4 FXO with 4 FXS ports.

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G100 VoIP Gateway


Digium’s G100 VoIP Gateway is a single port software-selectable T1/E1/PRI appliance that supports up to 30 concurrent calls.

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G200 VoIP Gateway


Digium’s G200 VoIP Gateway is a dual port software-selectable T1/E1/PRI appliance that supports up to 60 concurrent calls.

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G400 VoIP Gateway


Digium’s G400 VoIP Gateway is a 4-port software-selectable T1/E1/PRI appliance that supports up to 120 concurrent calls.

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G800 VoIP Gateway


Digium’s G800 VoIP Gateway is an 8-port software-selectable T1/E1/PRI appliance that supports up to 240 concurrent calls.

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VoIP Gateways by Digium

What Makes Digium Gateways So Reliable?

Digium IP Media Gateways are industrial grade high-performance appliances. The combination of a state of the art embedded hardware architecture and a software architecture built upon the Asterisk communications engine gives the G-Series its rock-solid reliability.

Digium is the global leader in the manufacture of telephony interfaces cards. Companies have come to trust Digium quality which has been ISO 9000 certified since 2008. When we designed our VoIP Gateway appliances we built upon our years of experience engineering high-quality interfaces. We chose an embedded design so there are no moving parts. This means Digium Gateways run cool and last long.

Asterisk is the world's leading open source communications platform. Deployed in over 170 countries around the world from small businesses to Fortune 500 companies, Asterisk is the engine to use when your business needs to rely on its communications. By leveraging the power of Asterisk, Digium is able to engineer gateways with amazing performance. And, because Asterisk is open source, Digium gateways provide high quality media conversion at an extremely compelling price-point, making Digium Gateways the best value on the gateway market. 

Easy to configure VoIP Gateways

Easiest gateways to configure

Asterisk-based VoIP gateways

Built on the powerful Asterisk communications engine

Reliable VoIP gateways

State of the art embedded design for dependable reliability

Best value VoIP gateways

Best value in business media Gateways

Customer Quotes Icon

Customer Quotes

  • "Setting up the G200 was extremely easy compared to doing it with other gateways. I'm spoiled now! Digium has really set the bar high. Their new gateways make it incredibly easy to connect older TDM phone systems with SIP services."
    Tim Banks - Project Resource Solutions
  • "The new gateways provide more options to meet our customers’ needs and offer reliable communications for larger installations. In addition, the flexibility of the open API in Digium’s gateways enables xCALLY to offer full integration between our Asterisk Call Center deployments and the gateways. This is the tightest integration possible for our customer applications."
    Diego Gosmar - CEO of Xenialab
  • "I was amazed by the simplicity of the configuration of the G101. The flow of the configuration menus is natural, intuitive and logical. Compared to previously installed products, it seems too simple! It was up and running in 3 minutes."
    Brice Ferrandes - AccessIP France

Digium Gateways Provide SIP Trunking to Legacy PBX

Bring the cost savings of VoIP to your legacy PBX with the powerful combination of a Digium IP Media Gateway and Digium SIP Trunking. The gateway acts as a bridge connecting the legacy system through a PRI interface to SIP trunks through your existing internet connection. Digium Gateways instantly upgrade a legacy phone system, allowing it to use a SIP trunk out to an ITSP; while Digium SIP Trunking reduces long-term telephony costs by replacing traditional phone lines.

There are several immediate advantages to preserving a current legacy infrastructure and eliminating expensive T1 lines in favor of cost-effective Digium SIP trunks.

SIP Trunking Piggy Bank

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