Wow.... Check this out!

[skunked]

Originally Posted by Hugh R

Some studios use them it's a $100 replaceable link IIRC

IIRC they're $70 now.

Originally Posted by flatbutt

Anyone know how the sensor works?

there is a small amount of electrical current running through the blade therefore when something conductive (finger) makes contact with the blade the cartridge will pop. Wet wood, metal and other conductive materials can cause it to stop as well.