I stand corrected on the temperature sensor. Apparently before 2000, there was a separate temp sensor that was required to be mounted in the plumbing. After 2000, this is build in and as Mark (mas) mentioned, can be seen in the cell (as a little white bump in the plastic).
This cold temp shut off occurs at 50 degrees, with a output reduction to 20% max between 50 - 60 degrees, similar to temperature compensation.
However, tphaggarty, you are correct in that at 50 degrees or below, the temp cut off activates and it doesn't matter what the salt level is... kinda.
You can increase the salt level to compensate (as Mark from Watermaid and I have explained), which in the event that you need to produce chlorine under cold water cut off, you can activate the superboost mode to override the cut off condition.