Studer A812 NAB Adapters won't come off.

[StuderStupid]

I recently acquired a Studer A812 with the NAB Adapters attached, long story short, I can't get them off. Any help here for the answer?
Note: The centre button does not push down....

 

[dminches]

@StuderStupid Press down on the metal ring and the adapters should pop out.

 

[StuderStupid]

@StuderStupid Press down on the metal ring and the adapters should pop out. View attachment 87143

YOU ARE BRILLIANT SIR, I guess me, not so much!.....lol....Thank You!!!!