Half truth. With embedded There is such a thing as an announcement only announcement.
Try this:
Create a sequential group.
Turn voicemail off. Have no fallback, no overflow.
Turn announcements on for the group.
1st announcement 5 seconds.
post announcement tone> silence.
Tick second announcement>
Wait before second announcement> 10 seconds
Tick repeat last announcement.
Wait before repeat> 10 seconds.
Add an unticked user for the group.
Using the extension that is a member of the group,
Record the announcement 1 for the group using *92<group number>#
Record the announcement 2 for the group using *93<group number>#
May the force be with you.