I will tell you how to solve the problem that the camera image does not come without answering the call. To solve this problem, we must register the RTSP address of the doorphone to the indoor unit as a monitor.
As you can see in the photo, we click on the monitor part of the interface of the indoor unit. In the Device number field, we write the IP address of the doorphone. Then we write the name we want to give to the device in the Device Name field. Then we add the RTSP address. The issue we need to pay attention to here is that the IP address written in the RTSP address is the IP address of the bell panel. Then, we enter the information we use when logging into the web interface of the device in the username and password sections. In this way, the problem will be solved.