Redmond, Wash. - Three more cellphone suppliers - Acer, Fujitsu, and ZTE - plan to offer smartphones based on the Windows Phone operating system, Microsoft announced.

The new companies' phones will use the OS's latest version, called Mango, which was announced yesterday. It will be available on new smartphones in the fall and will be available as a free download to phones based on the current Windows Phone 7 OS.

 The companies will join Nokia, which is still developing its first Windows-based phones, and current Windows 7 Phone suppliers Dell, HTC, LG and Samsung. In the U.S., Windows Phone 7 handsets are available from AT&T, T-Mobile and Sprint and will be available in the coming days from Verizon.