Why do some HP calculators have springs inside?

[Steve Simpkin]

(12-29-2022 05:55 AM)lvt Wrote:  OK so my 12CP doesn't have springs but it has a quartz crystal, I wonder what the quartz crystal does in the calculator? There is neither digital clock nor chronometer function.

The only reason I would think is that the quartz crystal has something to do with the screen's adjustable contrast?

If it is similar to the HP 35s (which uses the same Sunplus CPU) the crystal is used as a RTC oscillator and is used for display refresh and keyboard scanning.

https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=130623