[Koshkin]

I think the most interesting feature of old desktop calculators was the use of the 'magnetostrictive metal wire acoustic delay line' for memory.

[Johnny555]

That is super cool, I've never heard of acoustic memory before.

Using a transducer a series of acoustic pulses (bits) are inserted into one end of the wire. The pulse travels along the wire at the sound speed and reach the other end where the signal is "read"

2000 bits with 6.5m of wire. You could make a 128GB flash card equivalent with only 416,000 km of wire (a bit over the distance from the Earth to the Moon)

[jonsen]

In fact the pulse travelled slower than the speed of sound. Thereby fitting more bits on the same length of wire. The transducer twisted the wire, so a rotational pulse spiraled down the wire. This takes longer time than a purely axial sound pulse.