Use a transistor for Ring instead of a second pot

[tbertels]

Instead of using a second MCP41100, I used an NPN transistor and a 50k resistor.

Here's what it looks like:

L1 to C1 were not needed in my case as they were already included in the small 12V converter.

Then I can simply use
digitalWrite(ringPin, HIGH)
or
digitalWrite(ringPin, LOW)
to trigger the ring on and off.