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          An Aluminum CPU

    Here we have a complicated piece of hardware... real hardware. It's made of Aluminum, and it must have served the US Air Force well in its time.
Front view Back view
Click a photo to enlarge
    This contraption is a Computer, Air navigation, Dead Reckoning, Type CPU-26 A/P  (Backwards talk loves to the Military, Yoda the Jedi like). On the front it has a sliding translucent window with a rotating compass dial and many incomprehensible markings. On the back it has a rotating disc that aligns with the scales below, full of equally incomprehensible markings. And there are some instructions: "If 'D2-D1' is +, drift is left in northern hemisphere"; "Use calibrated airspeed and press. alt. to obtain F Factor. Multiply F factor by TAS obtained with computer to obtain TAS corrected for compressibility"; and so on.
    This computer, built by the Felsenthal Instruments company sometime around 1960 (but based on a pre-WWII design), was aimed at the mobile individual, in any hemisphere. It placed the ability to swiftly implement numerous computations useful to a pilot in a lightweight, handheld unit. All without batteries or blue screens.
    Here are some more pictures. Click the photo of the case to see some additional useful instructions. Close-up of back  Vinyl case
Click a photo to enlarge
Exhibit provenance:
    I bought this item in an "antique mall" in Folsom, California.

More info:
    http://en.wikipedia.org/wiki/E6B (the E6B is a common variant of this type of computer)
    An E6B Manual is available here.

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