Digium, whose open source Asterisk IP PBX spawned a host of start-ups that commercialize the software, has bought up one of them because it has a better user interface than Digium’s.

Digium has bought Switchvox because users without deep technical knowledge can provision it for small businesses, the company says. Digium’s own interface is meant for a trained administrator and poses more difficulties for the uninitiated.

In addition to the friendlier user interface, the Switchvox PBX supports business applications such as CRM software so customers can make calls from within the applications. It can also link to Google Maps to display the locations of contacts in the PBX phone book. The PBX shows presence information about individuals on PBX extensions.

Switchvox’s gear supports as many as 500 extensions while Digium’s supports as many as 50, so the purchase gives Digium the ability to support larger customers.

Digium won’t say how much it paid for Switchvox, but the deal seems to be part of Digium’s strategy to sell to a mass market, not just to open source aficionados, the company has said. Another goal helped by this deal is to sell more PBXs to small and midsize businesses.

To that end, Digium has taken $13.8 million in venture funding to promote its name and package its products to boost sales. Since it got the money last August, it has named a new CEO and issued AsteriskNOW, a streamlined version of Asterisk with a user interface intended to get the PBX up and running in a small business in half an hour.

It has also partnered with open source router vendor Vyatta to develop a PBX with WAN ports as well as a firewall.

Digium and Switchvox gear is built on Asterisk, a full-function IP PBX that includes call control, voice mail, and support for H.323, SIP and MGCP VoIP protocols. The system supports standards-based Session Initiation Protocol phones and can be an IP add-on to legacy PBXs from such makers as Lucent, Nortel or Siemens. Asterisk supports ISDN trunking and the Q.SIG protocol for such interconnects.

Digium says it will retain all 15 Switchvox employees.

Other competitors that base their PBXs on Asterisk software include Aspect Software, The VoIP Connection and Critical Links.