Huion uses the name "PenTech" for their EMR pen technology and even has version numbers to help it has evolved over the years.
Much more here from Huion:
PenTech 4.0
Passive EMR
Adds a chip to the Stylus. Introduced in 2024 with the launch of the Kamvas Pro 19 and Kamvas Pro 27. Significant improvement over PenTech 3.x. Wider pressure range, much better pressure handling.
PenTech 3.0+
Passive EMR
Huion states: - "more linear pressure sensitivity" - "lower IAF"
PenTech 3.0
Passive EMR
Pressure now detected through a pressure sensor instead of relying on moving the ferrite core. This is a more reliable design and is how Wacom has been doing it for decades.
PenTech 2.0
Passive EMR
Pen no longer has battery. Pen gets power from the tablet.
PenTech 1.1
Active EMR
Pen has a rechargeable battery.
PenTech 1.0
Active EMR
Pen has a replaceable battery.