Robison's Manual of radio telegraphy and telephony for the use of naval electricians (1918)
Robison, S. S. (Samuel Shelburne), b. 1867, United States Naval Institute, Todd, David Wooster, Hooper, Stanford Caldwell · Annapolis, Md. : The United States Naval Institute · leaf 27
Fig. 14a.—Closed-Core Transformer (current in A B falling). <- ^ … 1 Fig. 14b.—Open-Core, Step-Down Transformer or Induction Coil(current in A B rising). C
