Here Ralf Hütter plays a Mattel’s Bee Gees Rhythm Machine, a toy battery-powered keyboard released in 1978.
Karl Bartos employs a Dubreq-manufactured stylophone, a miniature synth played by touching a wire-connected stylus to metallic contacts.
Wolfgang Flür is presumably engaged with a custom-made drumming panel, just like they used at a larger scale in both studio and concerts since 1971. Most likely it only triggers on/off, without pressure sensitivity.
It’s not clear what calculator model Florian Schneider is using there. It’s known that Casio FX-501P was used by Kraftwerk for this very track, but the live instrument looks rather differently.
However! In marketing for ‘Computer World’, Kraftwerk have commissioned a branded calculator model from Casio, based on the VL-80 which played musical notes with its number keys; and they included a booklet with the instruction for playing Kraftwerk’s popular tunes on the unit, including ‘Taschenrechner’ proper.
Curiously, in the very same 1981 year Casio have released VL-1, their quite famous home synthesizer/sequencer keyboard combined with a calculator, sold for 70$. It was the first in their VL-Tone product line, predating VL-80.
I looked for this album on cassette tape in all the record shops in our town because I didn’t have a record player. I finally found it in the supermarket and I was so happy. I think I still have the cassette somewhere in the basement.