Diehl Combitron Desktop Electronic Calculator
Diehl Combitron S
(Note: Unit pictured is missing the clear plastic piece that provides an
edge for tearing off printed paper tape)
Image Courtesy Martin Willemsen
The Combitron was the first all-electronic calculator from famous German
mechanical and electromechanical calculator manufacturer
Diehl Calclating Machine Company. Diehl was famous for beautifully-designed
mechanical and electromechanical machines, built in the tradition of
fine German craftsmanship.
The Combitron, introduced in late 1966, beneitted from Diehl's mechanical
prowess as far as the mechanical aspects of the machine were concerned, but
the electronics were another story.
The design of the electronic logic of the machine was contracted out to an
independent engineer in the US, specifically Southern California.
That contractor was Stanley Frankel, a brilliant
electronic engineer who previously worked on the Top Secret Manhattan Project,
the government project to develop the Atomic Bomb. Frankel was educated
as a nuclear physicist, but during his time on the Manhattan Project,
he became enthralled with calculating machines, especially machines that could
compute electronically. He was responsible for acquring IBM's earliest
programmable punched card calculating machines for the Manhattan
Project and developing programs for these primitive machines to speed the
extraordinarily complex calculations for modeling the critical atomic
fission reactions during the first few moments of an atomic detonation.
These calculations were used to prove that the bomb designs were going
to work, and were of major consequence in assuring that the US developed
a successful atomic weapon before the Nazis.
After his work on the Manhattan Project, and prior to the calculator design
work Frankel did for Diehl, he had worked on the design of a number of small
computer systems (including the Royal McBee/General Precision/Librascope LGP-30
and the Packard Bell PB-250), and also had developed the design of a pair of
first-generation transistorized electronic calculators, the
Smith Corona/Marchant (SCM)
Cogito 240 and
The design for the Diehl Combitron grew from a prototype machine that
Frankel had built in his home workshop. This prototype he called NIC-NAC.
NIC-NAC was based on the fairly new concept of a microcoded architecture,
utilizing magnetostrictive delay lines for storing both the microcode
and the working registers. A pair of telephone dials were used to hand-load
the microcode into the microcode delay line, and an oscilloscope was used
to observe the input and results of calculations. Frankel shopped his design
around, trying to find a calculator company he could sell the design to.
Through his earlier relationship with SCM, Diehl found out about it,
and a deal was made for Frankel to go to Germany and develop Diehl's first
electronic calculator based on the NIC-NAC design, which became the
The Combitron, and the later Combitron-S (which added more more program
and memory storage, as well as the ability to interace to external devices
such as a punched paper tape reader and punch), were learn-mode programmable,
and had sophisticated decision-making and branching capabilities. The machines
offered the usual four math functions, along with one-key automatic
square root calculations. Both machines utilized a built-in digit wheel per
column line-at-a-time printer for output. The microcode is loaded from
a punched stainless steel tape at power-on time, meaning that it takes a short
time to "boot up" when first powered on.
These machines utilize fully-transistorized logic with amazingly few
transistors due to their highly efficient design.
The machine pictured is a Combitron S model. The museum has recently acquired
a Combitron S that is currently undergoing restoration and documentation
for an upcoming exhibit. At this time, the museum is looking for a Combitron
model to compliment the Combitron S. The machines are visually identical
other than a small peripheral connector on the left side of the machine, toward
the front, on the Combitron S.