https://garrett.com/sites/default/files ... _sheet.pdf
Additionally the website has, amongst many videos (some being detector model-specific), a short video covering the same subject of coil types:
https://garrett.com/sport/support#howtovideos
Just to be clear, I am not trying a subtle push of Garrett detectors! I merely found the search coil PDF particularly useful for differentiating coil types, and understanding the associated jargon.
I am sure there are many other resources out there for learning about such stuff, and I will likely eventually find them, but for now this PDF has been useful for me! I hope it will prove useful to other beginners too.
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