The Systron-Donner Series 80, first shipped in 1964, is the Cadillac of general-purpose analog computers. It is transistor based instead of tube based as most of its contemporary analog computers, it offers a ± 100V computing range providing 3-4 digit accuracy, and it offers a rich set of analog functions. A Series 80 weighs about 700 pounds. It has a removable program panel; on the left is a picture of it with and without the program installed.
Our Series 80 is fully functional; the pictures show it executing (perhaps simulating a new Centaur processor function invention). It is fully loaded with all of the optional features: 8 function generator cards, 220 10-turn potentiometers, digital voltmeter, and 42 computing modules. The original price for this configuration in 1965 was over $60,000 (a price list is shown on the right). Also shown is a picture from Boeing of a SD 80 in a Boeing 707 being used to analyze data for the SST program.
While the Systron-Donner Series 80 is the oldest and rarest analog computer, this is the most modern and most available. The Comdyna GP-6, shown in Figure 1, is a relatively small and inexpensive computer that can usually be found on ebay. It was manufactured from 1968 to 2004. The Comdyna GP-10 is a very similar device, but optimized for analog signal processing applications. Figures 2-4 show our four GP-10s in a special case where they share power supply and control. This type of system is often used in synthesized music applications.
These computers are fairly limited in capacity, but are perfect for classrom and breadboarding applications. I have my GP-6 set up to solve the differential equation
x'' = -x
The solution, of course, is a sine wave. (Since sin(x)' = cos(x), and cos(x)' = -sin(x)).
Unsuspecting engineers passing the museum are often dragged in for a demonstration of the principles of analog computing using this example on our working GP-6.