vintage elevators

[Carol Anne]

How were lifts in tall buildings controlled before the advent of microprocessors ? The lift in our building has been in constant use since 1960 and is now only being brought up to date with new electronic gear. Ie how could it memorise the sequence of calls made/floors chosen before electronics?

[thundercrack]

hi,
it probably didn't remember anything. you press a button, a relay engages the floor selected and a series of micro switches told the relay to slow the lift at the chosen floor, and another to tell it to stop. it would ignore other requests until the relay dropped out after mission completed. it would then take the next request and ignore all others until sequence complete again. just loads of relays and dozens of micro switches, all mechanical and prone to failure.
hope your computer contolled new system doesn't crash and leave you all stranded between floors like the old system s used to.

[GRC]

Just to add to the previous (correct) answer that a microprocessor is just an electronic version of the relays, timers & switches of old. The new controls for your lift will "memorise" what to do next in exactly the same way only with no moving parts!