TRS-80 100/102/WP 2 Disk format

[david__schmidt]

Edit: I found what I was looking for in the manuals that Dave Dunfield has made available: http://www.classiccmp.org/dunfield/kyocera/index.htm
Specifically, http://www.classiccmp.org/dunfield/kyocera/portdisk.pdf and http://www.classiccmp.org/dunfield/kyocera/disksoft.pdf.

I've got a few disks from the portable Tandy floppy drive here. I'm interested in some low-level formatting details. So far from the flux change histogram, I can tell they're FM-encoded, but not much else. I found this info about the format:

Storage capacity (Formatted)
Per disk 202.24K bytes
Per track 2,560 bytes
Per hard sector 1,280 bytes

Disk
Number of surface 1
Number of memory blocks

Total number of tracks 80
Total number of hard sectors 160

Recording systems
Recording method FM
Recording density 4,064 BPI
Track density 135 TPI
Data transfer rate 125k bits/sec.

Process time
Average access time 710 ms
Track-to-track 40 ms
Settling time 20ms
Motor start time 1s

Rotational speed 300 rpm

Number of Indices 2
​

My first question is: how is a 3.5" disk "hard-sectored?" There's no index holes on 3.5" media or sensors on any 3.5" drives... surely they don't mean the same thing as in 5.25" or 8" media/drives?