The AC12 fooled me. It doesn't send any messages when first powered up. You have to configure it and then it will start sending messages.
Here is my first hookup of the AC12.
The AC12 is attached with double sided carpet tape, and everything else is soldered to the Radio Shack perf board. I forced the 2mm AC12 connector into the .1" holes, put ferrite beads on all four inputs and added a coin cell battery. I'm using a "smart" cable to convert from USB to TTL serial. I don’t show the back side, but the wiring consists of bare wire running along the copper pads, soldered at the connections.
FTDI's TTL-232R converter cable makes interfacing easy. It is available from Mauser for $20.