Book 3 — Signal Telegraph with Green and Red Lights
Reading edition
By arranging a circuit with batteries, lights, and keys, as shown in the diagram, a signal telegraph may be made that will afford much pleasure to boys and may be used for practical purposes. The keys A and B are wired into the circuit with a battery C and a red and a green incandescent lamp. A simple set of signals may be devised easily so that messages may be sent in the code.—James R. Townsend, Itasca, Texas.