Friden 132 Electronic Calculator with acoustic memory

Nice article and youtube video about the 1963 Friden electronic calculator. The calculator featured RPN and a 4-level stack. The neat thing is how the memory was implemented - as a “recirculating audio acoustic memory” using a spiral of piano wire. The author states that it takes about of 1/100 of a second for the bits to traverse the spiral. Assuming a nominal propagation velocity of 5000 m/s, that’s a 50 meter spiral.

https://www.eeweb.com/profile/max-maxfield/articles/when-the-friden-132-electronic-calculator-was-state-of-the-art

The same ;acoustic memory’ concept is/was used for the reverb effect in guitar amps, although the guitar reverb springs have the form factor of a traditional long-and-skinny ‘screen door’ spring. If you’ve ever bumped a guitar amp with it cranked up and reverb on, you’ll cover your ears when the spring transducers crash. Good spring reverb unit pic and demo of crashing springs in this video

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