casio as-l

the as-l is a rather interesting old mains desktop calculator from casio. it has a 12 digit nixie tube display and arranges the keys on the right rather than below giving the machine a rather long and odd shape.

the shape is interesting because it allows room for papers and documents on a desk below it rather than, as is now usual, to the side.

the circuit inside is all on one board. the back of the top is the keyboard circuit.

here is the four chip cpu of the machine. the other chips are the display circuitry and the microcode rom.

twelve small nixie tubes provide the display. to the left a small extra neon is present to display the "-" for negative numbers.

this is the back of the keyboard and exhibits engineering design of something built to last. there is no mechanical nor electrical contact between the keys and the circuit (click image for close-up).

operation is by reed proximity switches (the glass tubes). inside sealed glass tubes, two small contacts connect in the presence of a magnetic field. the keys themselves have a small magnet on the ends their travel which trigger the reed relays.

interestingly, when i acquired the machine the key travel was somewhat stiff with age, but fully functional. i lubricated the keys using precision teflon grease (not oil!) and they were soon restored to their original tactile lightweight response.