by Alan Wexelblat
I attended a talk given by Randy Katz (Department Chair of EECS at Berkeley) at MIT last week. As the title suggests, it was a fast review of communications technologies. The talk was based on a first-year course Katz teaches at Berkeley.
Much of the talk (and the course, presumably) focuses on well-known dead media, such as the Nipkow disk. Below, I extract some of Katz's more uncommon remarks on other dead media. Some of the most interesting parts of the talk were Katz's suggestions on how to organize study of dead media.
Katz suggests a framework based on the role of government. His argument is that communications technologies have historically been seen as ways to extend the power of the existing power structure (kings, nation- states, business cartels) to remote locations, and to that end, funding has been selectively given or withheld based on perceived power circumstances. One well-known example, of course, is the granting of a state monopoly to the entity that became AT&T.
Katz argues that we see in the history of many media a recurring pattern of invention (most often by tinkerers, not scientists/researchers) leading to efforts to get state sponsorship for R&D. Many media die at this point, if the state refuses support. If the state grants support then the medium lives, at least for a time.
This approach also speaks to the question of why/when/how media die. Katz identifies three methods:
(1) "creative destruction" (in which a new medium destroys an old one, as the telegraph destroyed the pony express);
(2) "withdrawal of state favor" (as when Minitel finally died after the French government withdrew its support); and
(3) "market-driven death" (Betamax videotape).
Specific dead media (and notes of interest) mentioned in Katz's talk:
Muscle-powered messengers (foot and horse):
490 BC, Phidippides runs from Marathon to Athens with news of a battle.
By 14 AD, the Romans have set up a network of relay runners. The Roman Relay is the first known example of express mail. Normal messages were carried at the approximate rate of 50 miles/day, but express mail was marked differently and carried approximately twice as far. This is the source of the phrase "post haste" which was the marking carried on the express messages.
By 1280 AD, Kublai Khan had set up the first network of horse-using message relays. This medium finally dies about 400 years later when the Pony Express is retired (1860s).
Pony Express riders covered 150-200 mi/day. The longest ride was by 14-year-old "Buffalo Bill" Cody, who managed 384 miles in one day (ouch!).
The Pony Express record time for a message was 7 days, 17 hours. The message was Lincoln's Inaugural address (March 4, 1861).
Visual messaging media:
Visual messages began with various heliographic systems before recorded history (the Aztecs apparently had such a system, as did many nomadic tribes). (((bruces remarks: "Aztec Heliography??" We must know more!)))
The first regularized visual signalling system was the Howe code, which was commissioned by the British Royal Navy in 1790. Howe's system used 10 colored flags and a code book containing 260 entries. The goal, of course, was to be able to signal friends without giving away the orders to watching foes.
Howe revived work which was apparently originated by the fire beacons in Greece. This system was first written down in 150BC by an historian named Polybius. This is the first documented system for relaying messages reliably. The Polybius system consisted of five torches on each of two towers. These were interpreted as the rows and columns of a matrix which had 25 elements; the Greek alphabet had 24 letters.
Polybius' writings include the first known instances of flow control, handshaking protocols and error correction. These procedures were learned by operators through an apprenticeship program. If there were written manuals they have not survived to modern days.
The French optical telegraph consisted of a tower surmounted by a large three-segmented wooden armature. The inventor, Claude Chappe, was funded by the French military and developed a code whereby arm positions every 45 degrees were defined and mapped to characters. Thus, users could make shapes such as
| | \ /+\
+----+----+ and +
[ASCII graphics don't really do it justice.]
Initially, the system operated inside Paris only. Napoleon extended it as he conquered territory. By 1814, the system was contiguous from Belgium through France to Italy. By 1853, there were 556 stations covering a diameter of almost 3000 miles.
The system depended on the operator seeing that other towers had successfully copied his tower's position. Then he would change his armature. Thus, messages rippled through the network in a one-character-at-a-time relay fashion. The effective data rate was 1 character every 30 seconds over a visible distance of approximately 10 miles between towers.
The optical telegraph lasted until about the 1850s, when it was supplanted by the electrical telegraph.
Alan Wexelblat (firstname.lastname@example.org)