Fritz TR064 - detecting active call (not only ringing)

most likely it’s my fault: How may I detect the event active call after ringing?

Detecting ringing events with
-> {fritzboxtr064=“callmonitor_ringing” } I defined a Switch fboxInRinging and
-> {fritzboxtr064=“callmonitor_outgoing” } I defined a Switch fboxOutRinging
is working fine in my rule.

When an incomming call e.g. is detected ‘fboxInRinging’ immediately changes to ON.
But when the pysically ringing ends and the phone call is still active (connection established, someone is speaking…) the ringing event does not switch back to OFF. Only when the active call is terminated then ‘fboxInRinging’ switches back to OFF - to late IMHO.

Background: I have a XFD (Extreme Feedback Display, 6m LED Stripe in my staircase) which should blinking fast during ringing, blinking smooth during active call and flash once when active call is terminated.
Any help kindly appreciated