Calix sold nearly $75 million in preferred stock this summer without publicly announcing the transaction, dampening speculation that the equipment vendor might go public any time soon.

The privately held company sold $74,978,125 worth of preferred stock, according to a July 11 filing with the U.S. Securities and Exchange Commission that is required to be made within 15 days of the transaction. Calix declined to identify the purchaser in the filing or comment for this story.

It’s not known whether the sale represents a new round of equity, diluting previous shares, or if the sale was made by an existing holder of preferred shares looking to cash out. But in either case, it runs contrary to widespread anticipation of an initial public offering of Calix stock this year.

“It’s something we’ve heard about for months--Calix going public as a major possibility,” said Erik Keith, Current Analysis analyst.

Calix’s only public announcement of funding to date came when it emerged from stealth mode in February 2003, trumpeting the closure of a $50-million E round that had brought its total funding to more than $260 million. That round, led by new investors TeleSoft Partners and Kinetic Ventures, won both firms a seat on Calix’s board of directors. But the most recent addition to the board--of Cisco veteran Don Listwin--was back in January.

Though Calix indicated in the July filing that it intends to use the new funds for “working capital,” the move will likely give rise to industry speculation regarding exactly what the vendor will do with the money.

“I’d have to think they’re going to buy [another company], and buy it for cash,” said one Wall Street analyst who requested anonymity.

Those who suspect Calix is shopping for acquisitions wonder if four-year-old Aktino is one possible target. In June, Calix announced it would resell Aktino's multiple-input/multiple-output (MIMO) and discrete multi-tone (DMT) access gear, which delivers long-reach DS-3 and Ethernet-over-copper services between 10 Mb/s to 50 Mb/s.

Aktino’s focus on bonded VDSL2 as a means to deliver Ethernet-over-copper might fit well with Calix’s own DSL business and defend against competitors such as Adtran and Zhone that are embracing Ethernet-over-copper. Ideally, the two vendors might be able to help each other win the kind of tier-one carrier customers they’ve been unable to snare on their own. For example, AT&T has shown interest in bonding VDSL2 for residential broadband and has expressed openness toward applying bonded copper toward wireless backhaul. Aktino’s technology could mesh well with that approach by focusing on business services. And Calix could lend the start-up more scale and stability.

“I’m not sure Aktino has the income statement or the balance sheet to do a deal with AT&T,” the analyst said. “They’d need someone at least the size of Calix to get them in the labs.”