Media gateways enable multimedia communications across networks using multiple transport protocols such as ATM and IP. They are essentially a translation unit between various telecommunications networks such as PSTN, NGN, 2G, 2.5G and 3G radio access networks or PBX. The focus of this article, however, will be the public switched telephone network (PSTN) and how it relates to PBX VoIP technologies.

How are PSTN and VoIP tied together?

Although PSTN is mostly a digital gateway, it was originally a network of fixed-line analog telephone systems. Some critics say that even its digital capabilities are starting to age in light of the VoIP revolution, and these same critics further speculate that the eventual role of PSTN will only be to serve the Internet and little else. The need for conventional phones will be eliminated over times as VoIP technology comes to predominate. For that to happen, every household will need to acquire a broadband connection of some type to replace the classic phone system. Although broadband penetration is growing, it is still not an available service in some areas, which means for the time being that the old reliable telephone is safe from extinction.

Primary uses for PSTN as a media gateway

In addition to dial-up or broadband users at home, PSTN is often used by businesses as well. Large companies often link to the PSTN through limited gateways, like a large private branch exchange system (PBX). VoIP PBX, known also as IPBX, is gaining in popularity because it works on an Intranet setup within the business. A PBX setup is more secure for most purposes and situations in which there might be an issue leveraging other forms of VoIP over an open line. In addition to heightened security, PBX offers the same features (e.g. voice mail with e-mail or other advanced features) you find with conventional Internet VoIP systems.

What’s offered with PSTN and PBX media gateways?

As with other types of VoIP, PBX on a PSTN offers the following standard features:

• Automated directory services
• Automatic ring back
• Call transfer
• Call forwarding
• Call waiting
• Call conferencing
• Custom greetings
• Department message boxes
• Hold music
  
• Speed dialing
• Voicemail
  

The future of VoIP and media gateway

PSTN will still be required for purposes other than just as a source for VoIP systems in the near future. Although the technology is growing rapidly, there remain other issues that make it impossible at this point to totally replace PSTN. As one example, not all VoIP programs and systems support important functions like 911 access. It must be said, however, that there very well may come a day when PSTN is strictly used as a media gateway, and nothing more.

See also:

• Benefits of GSM Gateways

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