HD Radio receivers and HD-n (n>1) subchannels

[Jim Hall]

On my Sony XDR-S3HD there are no pushbuttons for HD:  you tune to the
frequency and wait a second. If the radio detects HD, the display will
change to From WXXX to WXXX-1, then you turn the main tuning knob one click
to the right for the HD-2, another click for the HD-3 (and the display will
change to WXXX-2 and WXXX-3).



Are existing HD receivers able to decode this extra bit-stream? If so,
how does the listener select it? My understanding is that HD receivers
are equipped with HD-1, HD-2, and HD-3 pushbuttons. If there is no
HD-4 button, is one of the main-bit-stream subchannels sacrificed if
you tune to a station that is transmitting the extra bit stream? If
yes, is the sacrificed channel always HD-3? That is, if a station
chooses to use the extra bit stream, is the normal HD-3 channel always
the one sacrificed? Or is there, perhaps, just one HD-channel
pushbutton that, through repeated presses, cycles through all of the
HD subchannels that the selected station is transmitting?