File:Telephony Class NGM-v31-p357.jpg
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Size of this preview: 800 × 490 pixels. Other resolutions: 320 × 196 pixels | 640 × 392 pixels | 1,024 × 627 pixels | 1,280 × 784 pixels | 2,403 × 1,472 pixels.
Original file (2,403 × 1,472 pixels, file size: 1.56 MB, MIME type: image/jpeg)
Categories:
- Military communications equipment
- Black and white photographs of sitting men
- Black and white photographs of classrooms
- National Geographic Magazine, April 1917
- Military training
- History of military education
- World War I military communications
- Telephones in the United States
- Blackboards in the United States