Telegraph

A Telegraph is a technology around using devices for transmitting and receiving messages over long distances. This is different from a Semaphore, which transmits messages in one direction. A telegraph requires a set of fixed installations. Usually distances between stations is a kilometer or more, depending on the technology. Telegraph systems use a system of encoding messages before transmitting messages and the rate is usually slow, a few words per minute. Depending on the message encoding each message may contain more information.

There are four general forms of telegraph systems, in the general order of their invention:

An auditory telegraph (TL–0) uses a system of sounds to transmit information. Such a system uses mechanical sound makers like drums or natural generated sounds like whistles or other kinds of vocalizations. In some environments, like underwater, sounds can carry for hundreds or thousands of kilometers.

An optical telegraph (TL–1) uses mechanical system of paddles or arms to show characters, or uses lights or series of lights. These are mounted on towers or natural high points and require timing, observation skills, and clear weather to transmit messages. A heliograph is a version of the optical telegraph which uses mirrors to reflect sunlight to between stations.

A Mechanical Telegraph (TL–3), a refinement of the optical telegraph, uses complex mechanical components to precisely control signalling devices in order to transmit larger volumes of data quickly and efficiently.

An Electrical Telegraph (TL–4) connects two stations with a single wire, and uses a electromagnetic system to send signals between them. The range of transmission is limited only by ability to connect the transmission stations with wires and power the system. Distances of hundreds or thousands of kilometers are possible.

A wireless telegraph (TL–4) uses very early radio wave technologies to connect stations. There is no physical connection and depending upon the wavelength of radio selected, the communication can reach any where on the world or systems in orbit.

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