Did you ever figure out the solution to this? I have the exact same issue as OP, I also only have 2 terminals on the doorbell transformer, neither indicated as "load". The only complexity I have is I am connecting this to a front and side door, so I ran a 4 conductor wire from the ELK 930 to the doorbell transformer location. Probably overkill, but I wanted to put the 930 inside the panel. One added benefit is that my panel is connected to a dual battery backup, so even if the power goes out, the panel should announce which door has been "violated". I have the M1 configured as a non-alarm zone, but for some reason I can't get the zone to announcement...
