Other titles:CARRIER FREQUENCY TELEPHONE [Translation]
Summary: The principles of using carrier waves to convey multiple signals down a telephone line and examples of systems in use.
Description: (Reel 1) Diagrams and graphs explain how a high frequency wave can be modulated with a lower frequency signal, and show how filters are used to remove unwanted signals. There are some brief shots of the equipment used. A diagram shows the layout of a simple telephone system carrying two simultaneous conversations.
(Reel 2) Four systems developed for the German telephone network are shown, from a portable system (two men are seen setting it up at a roadside telephone pole) to a sophisticated set-up capable of handling many signals simultaneously. Graphs and diagrams show how each operates.
Alternative Title:CARRIER FREQUENCY TELEPHONE [Translation]
