Each theater has a "record line" set up on the sound console that can be patched to a video camera anywhere in the theater that you can get to with a tie line.
On the console in Matchbox 1, 2 and 3, the record line is controlled thru Matrix 4. On the console in Matchbox 4, the record line shows up as Matrix 7/8.
Directions for patching the signal to a camera -
Ensure that the appropriate matrix is sending signal
In the amp room, select the correct audio rack and find the REC L/R patch location
Using the patch cables, connect the REC L/R to the appropriate audio tie line
The audio tie lines are distributed throughout the theater and are all labeled numerically.
Once the audio lines are patched, you should have signal to the camera.
The matrixes are taking the same signal that is going to the mains, so if there is audio going to the mains, you should have audio to the camera.
You can verify the signal going to the tie line by plugging the patch cable in to the test amp port and checking volume in the rack thru the test amp.
The matrix master volume can be used to increase signal to the camera if necessary.