The First ATCU that gets an aircraft on radar
(eg. TWR upon departure) will identify the flight (eg 1NM from RWY, passing 2400 ft) So that controller will use
KLM123 identified (upon departure)...
The next controllers who will use the same radar system will usually say KLM123 radar contact...< instruction> ...
If the radar contact is lost...
KLM123 for radar identification, squawk ident...
KLM123 identified...
Thats the info we received in our ANSP...
Grtz
B