(きかい) A machine, particularly something with a motor in it which moves when activated. A computer is not a 機会, but a robot arm is. Emphasis is that the 機械 is one single big thing.
(きかい) More like the English word ‘equipment.’ Somewhat simpler or smaller than the other 機械 – and also more likely to come in a set than 機械. Examples of 器械 are:exercise equipment, scientific measuring devices, or those weird metal boxes you see on tops of mountains that measure earthquakes or weather. ZZZ
そうち Devices which are not particularly hi-tech and do not have moving parts: fire extinguishers, air-bags, defilibrators.
(きぐ) An appliance:anything from chain-saws to gas stoves to birth control devices like IUDs can be called 器具. Honestly, it’s really arbitrary!
(どうぐ) A tool which has no moving parts:fork, shovel, hammer, scissors.