What is Q Factor:
https://www.electronics-notes.com/articles/basic_concepts/q-quality-factor/basics-tutorial-formula.php
Ring Test Line Output Tranformer:
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/333-2/
Where to buy ?
https://anatekinstruments.com/collections/anatek-blue-ring-accessories
Manual
https://cdn.shopify.com/s/files/1/0915/6622/files/ARTest.pdf?v=1607104112
