- sync (the regular lines)
- positional track number, gray encoding (irregular lines)
- track fine tune (the block trio)
- fine track ID
After fine track ID is read correctly, the position is deemed correct, the RX head is turned off, and the TX head is turned on. This is the rx-tx gap. Then track data starts.
You can see them in this magnetic image - the whole 25% to 75% of the image is the servo signal area. The tracks are seen on the bottom 20%, top 80%:
https://commons.wikimedia.org/wiki/File:Aufnahme_einzelner_M...
Bottom to top:
After fine track ID is read correctly, the position is deemed correct, the RX head is turned off, and the TX head is turned on. This is the rx-tx gap. Then track data starts.