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Microsoft today announced that another Android hardware maker, Wistron Corp., has agreed to pay royalties to Microsoft for its use of Google’s mobile operating system — bowing to Microsoft’s claims that Android violates the Redmond company’s patents.

This is the fourth such announcement over the past two weeks. It might seem like a flurry of dealmaking, but it’s starting to look more like Microsoft may instead be slowly trotting out all the deals it has made to date, trying to ratchet up the pressure on other Android device makers.

The latest announcement comes with a new twist, mentioning not just Android but also Chrome, apparently expanding its patent claims to the other Google OS. Wistron, the former contract manufacturing unit of Acer, is a supplier to manufacturers of Google’s new Chromebook computers.

[FOLLOW-UP: Report: Microsoft chasing Samsung over Android, seeking $15 per phone]

Microsoft says in a news release that the Wistron deal “provides broad coverage under Microsoft’s patent portfolio for Wistron’s tablets, mobile phones, e-readers and other consumer devices running the Android or Chrome platform.” The release also includes the now-standard line, “Although the contents of the agreement have not been disclosed, the parties indicate that Microsoft will receive royalties from Wistron under the agreement.”

We’ve asked a Microsoft representative for more information about the company’s claims against Chrome, and we’ll update this post depending on the response.

The Redmond company announced its first Android patent deal more than a year ago, with its longtime mobile partner HTC.

In March this year, the company filed suit against Barnes & Noble and makers of its Nook e-reader over the use of Android in that device.

In late May, a report from Citi analyst Walter Pritchard said Microsoft is making $5 on every Android sold by HTC — and it’s asking for between $7.50 and $12.50 in negotiations with makers of other Android devices. That prompted some head-scratching around the industry, with one analyst estimating that Microsoft is making more on patent royalties from the HTC Android devices than from licensing its own Windows Phone.

On June 27, Microsoft announced an Android deal with military contractor General Dynamics Itronix. On June 29, Microsoft announced an Android deal covering Velocity Micro’s Android devices, including its Cruz Tablet. On June 30, the company announced an Android deal covering Onkyo Corp.’s Android tablets. Those were followed by the announcement of the deal with Wistron this morning.

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