Every scan of a unit barcode at a production station writes a row in the
barcode_track table. Whether that row is a plain “the unit passed here”
marker or a running time-in / time-out clock is decided by one setting: the station
view’s Avg Time.

What happens on a scan

• Avg Time not set (0). The scan writes an instant marker: timein and
  timeout both equal the scan moment and the row is already complete. It records
  that the unit was at the station — nothing more.
• Avg Time set (in seconds). The scan starts the clock: timein is
  the scan moment, and the row stays open (not complete) until the work is finished.

Scanning the same barcode again at the same station while its clock is open does not create a
second row — it restarts the open row’s timein. Scans from the
station views also write a barcode_track_audit row recording who scanned, on which
line, and the rack barcode if the unit was on a rack.

Scans that never open a clock

• A unit that has already been shipped / stored gets a marker row only.
• A rejected unit being repaired: the clock opens only when the reject code routes the unit
  back to this station. Scanning it at any other station writes a marker.

Stopping the clock

The row’s timeout is written, and the row marked complete, in one of three
ways:

• The operator accepts / completes the unit at the QC or packing step (the end-of-line scan).
• A repair (remake) is processed for the unit.
• The operator uses the station view’s Stop work time action — for when work
  is interrupted or put down without completing the unit.

The live work timer in the station view

When a timed scan opens, the station view (the QC monitor and the station barcode-track
views) shows a running work timer counting up from the scan, formatted as hours:minutes:seconds.
The timer turns red once the elapsed time passes the view’s Avg Time —
the expected seconds for work at that station — so an operator, and anyone watching the
screen, can see that a unit is taking longer than it should. The timer is not shown when the
company preference QC automatic accept is on, because nothing is then being timed at the
QC step.