The ring generator battery houses the self contained ring generator circuit, as well as the power regulator that steps down the 12v input to 5v to power the Raspberry Pi and other components in the other battery and installed in the phone (microphone, speaker, LEDs, etc). The circuit board in this side came together much more organically as I worked around unexpected needs for different things like the relay and L298N board. 

When I originally designed and printed the ring generator battery, I thought that I was going to be able to fit everything onto the circuit board, not anticipating the need for the L298N board. I designed a carrier for the L298N board that attached to the main housing using the top screw that holds the transformer in place.

I wanted to avoid as many non-permanent connections as possible to ensure there were no possibilities for things to come loose after the phone is installed. I removed the screw terminals and headers on the L298N board and directly soldered wires to the board.

This was connected directly to the circuit board, which had become quite cramped and components were installed on both sides.

The Raspberry Pi power regulator was installed on the back of the board along with the connections for the USB cable and button (ignore the resistor being used as a twist tie to hold the wires out of the way).

This board then slots into the fake battery housing.

The L298N is attached to its carrier and then fits into the open space below the circuit board.

The high voltage output wires from the transformer were then soldered to the wires connected to the jack being used for the bells. The wires were tucked into position and then the cover was screwed on. Staples didn't have any brown cardstock to print the label on, so I'm thinking I'll try to weather the label with coffee or something as it looks too new to me.