Squawk 7000

The transponder code a VFR flight sets in most of Europe when ATC has not given it a code of its own. It makes the aircraft visible on radar and to collision-avoidance systems such as TCAS without identifying it individually.

When a controller assigns a code (“squawk 4521”) you switch to it, and you return to 7000 when told “squawk VFR” or when you leave their service. In the USA the VFR code is 1200.