To wire an external 12V relay to the output port of an Axis camera, the GND and I/O1 pins should be used.
The GND (ground) provides the necessary electrical return path, and the I/O1 pin is used for the output signal to control the relay. According to Axis technical documentation, these connections allow for proper integration and control of external devices such as relays, ensuring they function correctly with the camera's output capabilities.