The help wanted sign is out at Overture Networks, which has $6 million in new venture capital and is finding a market for its technology that helps communications providers upgrade networks without having to uproot existing infrastructure.

Overture announced Monday it had closed on a $6 million round of financing. It’s the third round for the networking firm, following a $15 million round in 2002 and $3.4 million in 2001.

The additional financing will be used for technology development plus sales and marketing efforts, the company said.

Overture already has 25 customers and is growing at a “double-digit” rate per quarter, according to Jeff Reedy, Overture’s CEO.

“The additional capital will allow us to accelerate our ability to bring innovative solutions to companies and service providers looking to add Ethernet services cost effectively using any underlying infrastructure,” he said.

Overture develops platforms for packet-based digital networks. The technology has earned five patents in recent months. Its applications enable platforms to adjust and deliver fast Ethernet telecom services over packet networks. Overture also enables phone companies to track and bill for traditional “wire” services, such as voice and private lines that pass through packet networks.

The company says it is looking to hire sales, support and operations staff.

Morgenthaler Ventures and Intersouth Partners, which had already invested in Overture, led the new round. Other investors in the syndicate include Armada Ventures and Gray Ventures. Both had also invested in Overture.

“Overture Networks has perfected a way to send TDM (time dimension multiplexing) circuit traffic over the new packet infrastructure at the network’s edge,” said Drew Lanza, general partner of Morgenthaler Ventures, referring to traditional telephony infrastructure. “They’ve also got one of the best solutions for carrying IP packet traffic over TDM. What makes Overture such a capital-efficient fit for today’s business environment is that their technology allows carriers to generate new revenues and build on their legacy TDM services.”

John Glushik, a partner at Intersouth, will join Overture’s board.

“We believe this company is a leading example of the new model of cash-efficient startups,” Glushik said in a statement. “Overture has demonstrated a winning corporate vision and established itself as a clear market leader addressing the tremendous opportunity in this space.”

Overture Networks: www.overturenetworks.com