SAE AS394A

To specify minimum requirements for pressure, actuated Climb Indicators for use in aircraft, the operation of which may subject the instruments to the environmental conditions specified in paragraph 3.3. This Aeronautical Standard covers four (4) basic types of direct indicating instruments as follows: TYPE I - Range 0-2000 feet per minute climb and descent, TYPE II - Range 0-3000 feet per minute climb and descent, TYPE III - Range 0-4000 feet per minute climb and descent, TYPE IV - Range 0-6000 feet per minute climb and descent.