With the range to the enemy vital, range finders where easy to use and fairly accurate. They have also been used in such things as range finders for cameras as well as particular surveying jobs. Current from the cells act upon the set of resistors. One of these, R2, is variable and can be controlled by the use of the large knob on the side of the box. The scale of R2 is calibrated in degrees Celsius, and is carried with its dial.
Temperature is read directly from the scale.
Designed to be portable, this model is missing the carry strap. It measures a temperature range from 775-2800 degrees Celsius.