5.6. Secure Calls 
OpenScape Mobile Pro is capable of providing secure voice communication end-to-end.
If your system is configured to provide voice media security you will see a
Lock icon in your Android phone’s notification bar.
This indicates that you and the other party (or parties in the case of a
conference call) are in a secure connection.
The Lock icon is crossed out, indicating a connection that is not secure
when you (or your conference) are connected to a party whose device does not
support secure calls.
A tone is generated in addition to the crossed out lock icon when:
-
The call is transferred to someone who does not support secure calls.
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Someone is added to an existing conference who does not support secure calls (i.e., the conference is only secure if all participants are secure).
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You are placed on hold (or the party you called) and the media server providing "music on hold" does not support secure calls.
‣ Parent topic: Section 5. Handling Calls