Black box and Gadget

Black box noun - Equipment that records information about the performance of an aircraft during flight.

Gadget and black box are semantically related. In some cases you can use "Gadget" instead a noun phrase "Black box".

Gadget noun - An interesting and often novel device with a practical use.

Black box and gadget are semantically related. Sometimes you can use "Black box" instead a noun "Gadget".