Hi Thomas,
I have a HP 8902A and the command structure is very similar to the 8901A.
If this helps, here are the responses:
The response to 21.0SPCL was 1111.000
The response to 61.0 SPCL was 0.0
The Response to 61.2 SPCL was 0.0
Best of luck!
Joe, KN5U
