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TWO KINDS OF DEVICE ..... OR TWO KINDS OF DEVICES
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I don't see any real difference in meaning between "kinds" and "types". So far as I can tell, it's "two kinds of device", only, which would mean the same thing as "two types of device". In this context, "device" is actually being used as a continuous noun (believe it or not - meaning the continuum of all devices,) and so (in this context) wouldn't take a plural.

Rommie
Comments  
I wonder if my understanding towards this structure is correct.

" two kinds of device " means the same type of device in two different kinds

" two kinds of devices ' means different types of devices in two different kinds
 rommie's reply was promoted to an answer.