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What is a VoIP Gateway?

A VoIP Gateway allows you to convert between a legacy telephony connection, such as E1/T1/PRI and a modern VoIP connection using SIP. This is known as "digital gateway" because the voice media is converted between a digital TDM connection and a VoIP connection. The conversion can go from SIP to TDM, TDM to SIP or even SIP to SIP for the purposes of failover or transcoding. In a TDM-to-SIP deployment, the gateway significantly reduces operating costs by connecting a legacy business phone system with dynamic SIP trunking services. SIP-to-TDM deployments use the gateway to connect a modern SIP communications system with T1/E1/PRI service from legacy carriers. There are many applications for VoIP media gateways. 

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: 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.

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

A VoIP gateway may also be referred to by any of the following:

  • IP Media gateway

  • SIP gateway

  • Voice gateway

  • TDM gateway

  • PSTN gateway

  • PRI gateway

  • ISDN gateway

  • Digital Telephony gateway

The terms VoIP Gateway and IP Media Gateway are the most common names for this type of device.

Test Drive the Best GUI for VoIP Gateways

Want to know how easy to set up our gateways are? Watch this demo video to learn the basics then 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 to PRI conversion and more time to focus on what's important.

Take a Test Drive or contact us to learn more now.

VoIP Gateways by Digium

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

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. 

Digium VoIP Gateways with Asterisk

Digium G-Series Appliances

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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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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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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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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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.

VoIP Gateways for SIP Trunking

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

Using your existing legacy system lowers minimal investment.

Digium SIP Trunks will save thousands off your yearly telephony costs.

Adding new lines will be faster and cost much less than traditional phone lines.

The user experience remains unchanged and there is no retraining staff on new phones.

Find out more on how to deliver a higher standard of communications to your business with a Digium IP Media Gateway and Digium SIP Trunking. Learn More Now

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

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