Computermuseum der Fakultät Informatik                          german

Donner 3500

Type:         3500                                     <<<    >>>    ^^^
Manufacturer: Donner    
Technology:   Vacuum tubes (35 total)               
Year:         before 1960

Description on the advertisment:
"Portable 10-kg-analog computer, Model 3500. The first portable
independant analog computer available on the open market. Fits in your
lap, on your desk or your workbench! Contains 10 amplifier-channels as
well as all power supply and control circuits. For solving problems
that require a capacity of 30 amplifiers up to three Model 3500 analog
computers can be combined. The accuracy of each part is either 0.1% or
1%. The amplifiers are available as stabilized as well as in nonstabi-
lized versions. A complete range of peripherial devices is available."

According to the ad above this might be the world's first lap-top. The
analog computer is build exclusively with valves and contains 10
direct-current-amplifiers. Five of these can be used as integrators by
plugging in a capacitor. The other amplifiers can only work as
summators. The difference between integrators and the other amplifiers
is, that the capacitors in the integrators can be charged to a certain
starting voltage by setting the rotary switch to 'reset'.
The computer does not contain a multiplier or built-in summation
resistors. Rating of the summation-inputs is done by plugging resistors
in the programming-array.
As usual for analogue valve computers, the internal voltage is +/- 100V.

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