The flight manual of a Canadian DC-3 operator says
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The propeller anti icing system is installed in the airplane to prevent the formation of ice rather than to remove it when formed. The system should therefore be used whenever icing conditions are expected or suspected.
Windshield is also referred to as änti icing, the TCDS though refers to de icing. The Constellation manual advises to turn anti/de ice alcohol on once ice has begun to form.