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4. Projectors.
1. Rarely ever used except to attract observers' attention but could be used to transmit messages.
5. Ground Communications. 
(a) Couriers.
1. Ground.
2. Aerial.
a. Ground Couriers consist of:
Motor vehicles.
Bicycles.
Mounted.
Runners.
Ground couriers at present and in the future are used and are only necessary to assist aerial couriers.
(b) Aerial couriers consist of :
Airplanes.
Pigeons.
5. Aerial couriers are the most important and are the only sure methods of couriers communications. They are used for the following purposed:
(a) Delivery of important messages where speed,

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