OK, thank you, that is very helpful. It appears that in fact the 'handle' argument in the callback parameter is the number of responses that have been provided.

If I'm understanding this correctly, if I issue a read_multiple request, I will receive one READ_MULTIPLE_EVT for each characteristic that is read? I tried that once already and the handle reported in the callback didn't match any of the handles that I had requested in the read_multiple request. Is ...

I'd like to use the READ_MULTIPLE function, but the documentation (for version 4.4.3) doesn't describe the structure of the parameter supplied to the callback.