The phrase "a class of device" is correct and usable in written English.
It can be used when categorizing or describing a group of devices that share common characteristics or functions.
Example: "In the field of technology, a class of device known as smart speakers has gained immense popularity in recent years."
Alternatives: "a category of device" or "a type of device".
The mirror, its mount, and the other mechanical components are all made of silicon, putting the projector in a class of device called MEMS (microelectromechanical systems).
A lab-on-a-chip is a class of device that integrates and automates multiple laboratory techniques into a system that fits on a chip up to a maximum of a few square centimetres in size.
This week's App Smart was about apps you may like to try out on your new Android tablet — a class of device that is really making a splash in the mobile computing market to rival the iPad.
A growing category will be internet-connected monitors for "smart metering", video surveilance, maintenance, building automation, healthcare and consumer electronics – a class of device known as "machine-to-machine" (M2M) systems which communicate directly to other computers over the internet without the mediation of humans.
Artificial leaves aren't new: they're a class of device which passively converts light into power for various purposes.
It's a class of device that is aimed at simplicity of use, portability and the ability to allow the user to sit down and type pretty much wherever they are without having to wait for a full-scale notebook PC to boot up or wake up from sleep mode.
Digital computer, any of a class of devices capable of solving problems by processing information in discrete form.
Nuclear reactor, any of a class of devices that can initiate and control a self-sustaining series of nuclear fissions.
Electric motor, any of a class of devices that convert electrical energy to mechanical energy, usually by employing electromagnetic phenomena.
Battery, in electricity and electrochemistry, any of a class of devices that convert chemical energy directly into electrical energy.
Cyclotron, any of a class of devices that accelerates charged atomic or subatomic particles in a constant magnetic field.
