Wig-wag signaling
Wig-wag signaling was performed during daylight with a single flag tied to a hickory staff constructed in four-foot jointed sections. Flags were generally made of cotton, linen, or another lightweight fabric and were issued in the following sizes:
| Flag size (feet) | Flag background color | Center color | Center size (inches) |
|---|---|---|---|
| 6 x 6 | white | red | 24 x 24 |
| 6 x 6 | black | white | 24 x 24 |
| 4 x 4 | white | red | 16 x 16 |
| 4 x 4 | black | white | 16 x 16 |
| 4 x 4 | red | white | 16 x 16 |
| 2 x 2 | white | red | 8 x 8 |
| 2 x 2 | red | white | 8 x 8 |
The 4-foot flags with white backgrounds, mounted on 12 foot staffs, were most often used, although 2-foot flags were used when the flagman wanted to avoid enemy attention. For nighttime signaling, torches were copper cylinders, 18 inches long and 1.5 inches in diameter with a cotton wick.[
Each letter consisted of a combination of three basic motions. All began with the flagman holding his device vertically and motionless above his head. The first motion was initiated by bringing the device downward on the signalman's right side and then quickly returning it to its upright position. Motion number 2 involved bringing the device down on the left side and then returning it to the starting position. The third motion required lowering the device in front of the signalman, then restoring it to its vertical position. A flash demo can be found here
Ciphers
Since aerial telegraphy was sometimes conducted within the clear sight of the enemy, security was a major problem. The Signal Corps introduced a cipher disc, a simple device that allowed the encryption of text. Two concentric discs were inscribed with letters and their numerical equivalents. The sending and receiving party had to agree on the specific alignment between the two discs, ensuring that both parties had identical alignment. To encipher a message, the signal officer selected an "adjustment letter" on the inner disc and then made this letter correspond with a preselected numerical code or "key number" on the outer disc. The signal officer would typically give the key numbers to the flagmen without revealing the plain text version of the message. Although this method of encryption was primitive by modern standards, there is no record that the Confederates ever deciphered a Union message that had been processed in this manner. A more complex system in which four concentric discs were used was invented by Sergeant Francis M. Metcalf and modified by Captain Lemuel B. Norton, but it did not receive widespread adoption.
More information can be found in these links:
bravenet.com