What is the J4 on the PA01-0020-0xxx board for?
ICS090 series camclosures (ALL models)
ICS series Camclosures have been obsolete and there is no longer references to the board level components.
The J4 junction on the PA01-0020-0xxx board inside the back box of the ICS090 camclosures is for providing a test output for video. This outputs, via an RCA jack, composite video.
The original tester device that would work is the CST100 or CST150. Either of these could be plugged into the J4 to get video for testing purposes while at the local camera on site.