olemus
seadme järjestikune alamosa

Wiktionary:
2. one of the portions of a device (such as a rocket or thermonuclear weapon) which are used or activated in a particular order, one after another
10. (electronics) the number of an electronic circuit’s block, such as a filter, an amplifier, etc.

3 stage -- kolmeastmeline
amplifier stage -- võimendusaste
input stage -- sisendaste
multistage -- mitmeastmeline
output stage -- väljundaste

näiteid
https://en.wikipedia.org/wiki/Multistage_amplifier

https://en.wikipedia.org/wiki/Multistage_rocket