The C /F exchange button will allow you to switch between temperature displays of Celsius (C) or Fahrenheit (F).
C / F Exchange
The Max/Min memory records the temperature over a certain period of time and stores it to memory.
Max/Min Reading Memory
The ice point alert will alert you when the temperature approaches the freezing point.
Freeze Alert
The dual display feature shows the current humidity level as well as the current temperature.
Dual Display
The external sensor on the 810E will give a temperature only reading at an outdoor or secondary location.
External Sensor
Humidity Sensor