What are the necessary parameters? That’s is to say, if we don’t set them right, the radio can't communicate with other radios.
What are the necessary parameters of analog radio communication? Frequency and CTCSS/DCS.
Frequency is the most basic and necessary parameter. It makes no sense to talk about radio communication apart from frequency. So if we want to make two radio communicate, the frequency we must set same. This is the first thing we need to do.
CTCSS and DCS are systems used to reduce the annoyance of listening to other users on a shared two-way radio communications channel. When we want to connect the repeater, it will be the necessary element.
We set an analog radio to communicate with another one directly. we can set it as the photo "Radio - Radio".
If we want to connect the repeater, and we know the repeater information, we can set it as the photo "Radio - Repeater - Radio".
About the CTCSS/DCS, we can check this blog.