Gateway v. PCI Cards, What's The Difference?


We still have many customers who still use PRI technology. And from a price, quality, and feature perspective, PRI’s are hard to beat. In the Phoenix, Arizona Metro area, where Chromis Technology is based, we see prices anywhere from $350 – $500 per month per PRI depending on the carrier/features. A typical T1 PRI carries up to 23 channels of voice so price per channel is anywhere from $15 – $22 which is very competitive.

So then the decision becomes which technology to use to bring your PRI into your Asterisk or Switchvox solution. Luckily, Digium has you covered on both angles by offering both external gateway products or PCI interface cards. Let’s look at what the differences are between the two.

The primary job of both a gateway or a PCI interface card is transcoding (Think of converting a CD to MP3 files, this is an example of transcoding). In the context of this article, the variety of transcoding we’re doing means taking a SIP signal and converting it to PRI signaling (or vice versa).

[![2PortGateway]( "Digium 1G200F Gateway")]( interface of the Digium 1G200F Gateway. Click to enlarge.
**A Digium gateway** is an external appliance that has its own user interface (GUI) that is similar to the award winning Switchvox interface. The Digium gateways come in single (1G100F) and dual port (1G200F) configurations. Digium gateways can be used with many different phone systems to convert TDM T1 (PRI) to SIP signaling (or vice versa SIP to T1).

So let’s say you had an old Toshiba (or Nortel/Avaya/Panasonic/etc.) phone system, and you wanted to use SIP trunks, a gateway would allow you to bring those SIP trunks in to your non SIP speaking telephone system. In the Asterisk or Switchvox scenario, both are native SIP Software so a gateway is not necessary to act as a middleman.

However if you want to bring a PRI into your Asterisk or Switchvox installation, you’ll need a gateway or PCI card. A gateway would accept the PRI signaling from the service provider and convert it to SIP signaling that Asterisk or Switchvox could understand. The gateway contains hardware echo cancellation to eliminate echo problems that might occur.

1te220bfA PCI interface card takes the service provider’s T1 and plugs directly into the server via the card that’s inserted into a PCI (or PCI-Express) slot. These cards are specifically designed for Asterisk or Switchvox systems. Cards come in single, double, and quad spans. So you decide how many T1’s are you looking to bring into the system, then you pick your card span. The configuration is done by an administrator in the Asterisk command line or the Switchvox graphical user interface. (There is also an 8 port T1 card option for high density Asterisk installations. This card is currently not supported by Switchvox.)

It’s worth noting that you can also purchase cards that will interface with analog telephone lines as well. Those PCI cards come in 4, 8, or 24 port configurations.

Analog and T1 PCI cards have optional hardware echo cancellation modules, which Chromis recommends on all installations, which offload echo cancellation from the system’s CPU to the dedicated CPU on the E.C. module.

If you still have questions about whether a gateway or PCI card is best for your solution, Chromis Technology can help! For a personalized quote or to ask us a question, please contact us or call us at 602.357.8070.