If the observation number must be more than 999 or the cycle number more than 99, or the channel number more than 99, the second format must be used. The file log will be Pooo.ADT or Pooooooo. Usually there is no risk for the tube at this voltage, even in case of bright illumination. Photons usually don't appear. Usually there is a risk for the tube at this voltage for bright illumination, but not for common observations.
Photons begin to be visible.
The user must control the flux on the TV control display and adjust the THT value with the observation brightness. The risk is maximum. It could be parallel or serial. For Thomson, this value is 256. For Thomson, this value is 256.