machine; machinery

be useful, serve / be valid, be usable (e.g. a coupon at a cash register)

operate (machinery)

maneuver, operate

simple, easy

simplicity, ease

器械: a device, an appliance, a mechanism / 機械: a machine, equipment, an apparatus / 器械: a utensil, a tool, an instrument / 器械: a tool for conducting a test or experiment or for measurement

operability

operator

remote control, remote operation (doing something from a distance)