Signals and Messages

Human societies operate on a scale larger than face-toface encounters. Signals and messages constitute the force that binds them together. Advancing technology provides improved methods for communicating at a distance.

Visual signals need a line of sight between sender and receiver. An observer whose viewpoint is at a given height above ground level can see to the range specified in the Horizon Table (p. LT49). Use the Size Modifier Table (p. B19) to convert between height and SM.

For two individuals, add the ranges for their respective SMs. If the distance between them is less than this, they can see each other. The same applies to an observer looking for a tall mast, lighthouse, mountain, etc.

Spotting a visual signal requires a Vision roll (p. B358).

Modifiers: Range modifiers (p. B550); +10 for a deliberate, unmistakable signal, as it counts as “in plain sight”; at TL4, the benefits of telescopic magnification (see Spyglass, p. 42); bonus for extra time (p. B346), if scanning slowly.

The following types of signals are available.

Beacon Fire (TL0). Customarily built in a high place. A TL1 society may set up a line of beacons on mountain peaks to relay a signal long distances. A typical beacon is a yard high and roughly hemispherical; add its SM +1 to Vision rolls. At night, fires become more visible; reverse the sign of the darkness penalty, giving a Vision bonus to see the fire. A beacon can carry only one message – usually “Here I am!” or “Danger!” Smoke Signal (TL0). The most famous example of smoke signals is their use by Native American tribes. Sent by building a smoky fire with green or wet wood; covering it with a blanket can interrupt the smoke, generating short puffs or long plumes, to carry several different messages. Smoke typically rises to 500-600 yards, giving a horizon of 45 miles. Lantern Balloons (TL3). Made from oiled rice paper on a bamboo frame, the lantern balloon was carried aloft by the heat from a wax candle burning inside it. In 15 minutes of flight, it could attain an altitude as great as 1,000 yards (SM +16; horizon 65 miles). It was used for military signaling at night, when it would get +10 to visibility. $10, 0.75 lb. Signal Flags (TL3). Improvised use of flags and other colored signals goes back at least to TL2; for example, Greek legend tells of ships using different-colored sails as signals. In the ninth century A.D., Byzantine emperor Leo VI discussed using signal flags at sea. Western European fleets in the later Middle Ages began to use similar codes. The British admiralty standardized naval signals in 1647. A typical flag is smaller than the man carrying it (add its SM -1 to Vision rolls), but stands out from the background (+10). Prices and weights vary. Flag one man can easily carry: $50, 3 lbs.

Loud noises can carry quite far, offering a means of signaling. Auditory signals aren’t limited to line of sight; sounds can diffract around bends, corners, or the curvature of the Earth, although this may distort them.

Each sound source has a standard audibility range (about 8 yards for a shout). This is the range at which it can be heard with an unmodified Hearing roll (p. B358).

Modifiers: -1 per doubling or +1 per halving of distance, relative to audibility range; +1 for a high-pitched sound (the equipment statistics below already account for this); -1 if the listener has no line of sight to the source; +1 for multiplying the number of sources set off at once by 10, +2 for 100 sources, and so on; half the extra time bonus (p. B346), rounded down, for repetitions (+1 for at least four, or +2 for 15 or more).

A loud or monotonously repeated noise can function as an alarm. Varying rhythms or melodies can carry genuine messages: military orders, guidance for mounted hunters, etc.

This list emphasizes instruments useful for signaling. Most of these – and many others – are also used for entertainment! See GURPS Low-Tech Companion 1 for a discussion of Musical Instrument skills.

Talking Drum (TL0). The instrument used to send messages through the African jungle. It’s held under one arm and struck with the other hand; pitch is adjusted by squeezing it. Played with Musical Instrument (Tuned Drum). Audibility range: 32 yards. $40, 2 lbs. Harp (TL1). The classic bardic instrument. Played with Musical Instrument (Harp). Audibility range: 4 yards. $600, 7 lbs.

Shofar (TL1). The horn of a sheep, used as a trumpet, as described in the Bible. Played with Musical Instrument (Horn). Audibility range: 16 yards. $80, 5 lbs.

Fife (TL2). A shrill, flute-like instrument, used by the Spartans – and by military marching bands of later centuries. Played with Musical Instrument (Flute). Audibility range: 16 yards. $100, 1 lb.

Trumpet (TL2). An early brass instrument, often long and straight rather than coiled up. Played with Musical Instrument (Horn). Audibility range: 32 yards. $200, 2 lbs.

Bagpipe (TL3). Best known in the Scots version, but forms of this instrument are found worldwide. Played with Musical Instrument (Bagpipe). Audibility range: 32 yards. $150, 8 lbs.

Church Bell (TL3). Cast from bronze, and used to summon people to worship – or to signal emergencies. No skill roll required; roll vs. ST+2 to ring loudly. Audibility range: 128 yards. Bells come in varied sizes; a 36” specimen is $20,000, 900 lbs. For other sizes, multiply cost and weight by the cube of bell height in yards. (Example: A 48” bell is 1.33 yards tall; the cube of 1.33 is 2.35. Cost is $20,000 x 2.35 = $47,000; weight is 900 lbs. x 2.35 = 2,115 lbs.) Doubling or halving height doubles or halves range.

Hunting Horn (TL3). Made of brass, and carried by huntsmen to signal the progress of a hunt. Played with Musical Instrument (Horn). Audibility range: 16 yards. $200, 2 lbs.

Kettledrums (TL3). Not the orchestral instrument, but a smaller one designed to be carried on a horse’s shoulders and played by the rider. Played with Musical Instrument (Tuned Drum). Audibility range: 32 yards. $250, 28 lbs.