Switching ADS-B on/off, when

[Stormy]

This week, I took my RB to EDDK to see what happens on the ground. Most signals disappear at touchdown, some of them at going onblock. ADS-B is mostly switched on at nose up during start.
How is this maintained? Is there any regulation for switching ADS-B on/off or is this airport depending.
Anybody knows somwthing about it?

Thanks for response.

[b744]

the transponder is normally switched on at/before engine start and then off when finally parked at the gate.
The functions of the old transponders were triggered by the act of taking off/landing by means of weight on wheels or oleo extension(silver bit on the undercarriage leg). These days the ground function is used by atc(ads part) but still uses the weight on wheels for the TCAS operation ie being seen on the displays inside other aircraft.
Not the best explanation but hope it helps
Rgds

[Stormy]

Thanks for your fast reply.
This would mean there is no human influence on switching it on or off?
How is it possible that I see an A320 and a B737 with ADS-B on until onblock?