Becker Centronic VarioControl VC420-II Notice De Montage Et D'utilisation page 36

Overwriting the master
Switch off the radio receiver's power supply and switch it back on again after
10 seconds, or briefly press the radio receiver's programming button.
▻ The radio receiver remains in programming mode for 3 minutes.
To ensure that the new master transmitter is programmed in
the desired radio receiver only, all other receivers which are
connected to the same power supply must be deactivated
from the programming mode. To do so, after switching the
power back on, execute a drive or stop command using the
transmitter for the given receivers.
Now press the programming button of the new master transmitter for 10
seconds.
▻ The receiver confirms.
► The new master transmitter is now programmed and the old master
transmitter deleted.
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