Railroad Archives Online
- CollectionE0482 - Great Northern Railway Historical Society Standard Signal Plans Collection
- Series003 - Great Northern Railway Company (U.S.)
- Subseries Level 1009 - Engineering Records
- Subseries Level 2008 - Physical plant drawing
- Subseries Level 3005 - Signals
- 83 more...
- Item167-96 - Great Northern Railway Standard Signal Plans; Ladder Clamps for Ground and Bridge or Bracket Signals, 1920
- Item167-97 - Great Northern Railway Standard Signal Plans; Mast, for Mechanical and Electrical Signals, 1919
- Item167-98 - Great Northern Railway Standard Signal Plans; Ladders, 1-Arm Electrical Ground Signal, 1920
- Item167-99 - Great Northern Railway Standard Signal Plans; Ladders, 2-Arm Electrical Ground Signal, 1920
- Item167-100 - Great Northern Railway Standard Signal Plans; Ladders, 3-Arm Electrical Ground Signal, 1920
- Item167-101 - Great Northern Railway Standard Signal Plans; Ladders, 3-Arm Electrical Bridge and Bracket Signal, 1920
- Item167-101A - Great Northern Railway Standard Signal Plans; Ladders, 2-Arm Electrical Bridge and Bracket Signal, Stay Clamps for 5-1/2 Inch Pipe, 1920
- Item167-102 - Great Northern Railway Standard Signal Plans; Ladder Parts, Electrical Signals, 1919
- Item167-103 - Great Northern Railway Standard Signal Plans; Ladder, Clamps and Stays, Electrical Signals, 1920
- 36 more...