Hand-held Calculators

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RFT 75

RFT minirex 75

RFT 75

Distinctive features: One of a series of models manufactured in the communist GDR (East Germany). Batteries recharged by inserting the calculator in the charging unit.

Technical details:
Display is 8 digits, red LED.


4.8v (4x rechargeable button cells).

Main integrated circuit - Texas Instruments TMS 0105NC, here dated 1973.

81 x 139 x 34 mm (3.2" x 5.5" x 1.3").


Made by
VEB Rohrenwerk Mulhausen,
in combination with
VEB Funkwerk Erfurt.
Made in GDR. ["German Democratic Republic, ie. East Germany]

The calculator batteries are recharged by plugging the calculator into the docking station.

In docking station
With docking station

The calculator plugged into the charging unit.

circuit board

The calculator alongside the charging unit.

On the bottom of the calculator is the plug to connect it to the charging unit, and also the on/off switch.

The calculator is secured to the charging unit by a captive finger screw from the back of the charging unit.


The circuit board with the Texas Instruments calculator chip.
Note the high-quality binding with cord of the wiring.

The unusual nickel-cadmium rechargeable button cells.

This calculator is from the middle of the period of the "Cold War" before the fall of the Berlin wall and the reunification of Eastern and Western Germany.

During the decades of separation between communist eastern Europe and the west, development of components often took different paths, as shown by the rechargeable cells which look very strange to us in the west.
The communist coutries lagged behind in chip technology, and so a Texas Instruments calculator chip has been used, which were relatively cheap by this time.

The binding of the wiring with cord is not something that was cost effective in a capitalist economy, but this feature of high-quality industrial wiring has been used in this product of a command economy.

The use of a docking unit seems a very logical and neat idea, yet they were very rarely used. The Advance 88 is another example, but the docking unit is much cruder.

Hand-held Calculators

Vintage Calculators

© Text & photographs copyright Nigel Tout   2000-2018  except where noted otherwise.