There is some question of how secure the signal is from this type of headset.
DECT technology uses encryption to protect the signal. DECT technology is a standard just like Bluetooth or wi-fi.
The Sennheiser headsets are actually more secure since they requires physical contact to make a connection.
Sennheiser’s wireless headsets meet the same security standards as all other DECT headsets.
However, the official DECT security list is a paid subscription which Sennheiser has not paid to have a listing on, which is why Sennheiser headsets are not currently listed.