OzRunways - R-NOT-S

[Jabiru7252]

Often I see aircraft identifying as R-NOT-S on Oz Runways. Sometimes it's doing 90kts down low, other times it's at FL30 and doing several hundred knots. Anybody know what the R-NOT-S means?

 

 

[Downunder]

What I see is "NO SEND".

 

 

[Thruster88]

As an android user I see NO SEND also. Presumably these pilots are on a secret  mission and don't want anyone to talk to them or they have just not configured their system to show their call sign?