Communications and telecommunications are always important to a city. The first type of communications was with runners (on foot or on horse). The need of something faster made them decide to use signals with fire. After a while they had the first code for using fire signals. On hills or mountains near the city there were special personnel for such communications.
Here is a sample of how the code was working: the alphabet was divided in 5 rows and 5 columns. So they used 2 groups of 5 fires to indicate which letter they wanted to transfer. They could transfer this way up to 20 or 25 words every hour. It was not very fast but it was working! The low speed forced them to use stenography with prearranged code. So the famous from the Usenet 'CUL8R' (see you later) is not such a new invention! :-) When Troy fell into the hands of the Greeks, the rest of Greece knew it in a day's time by using this system!
This type of communication with fire signals was also used in a simpler form. The time period was divided in hours and for each hour there was a predefined message. So if the fire was on at 12 o' clock it could mean 'send army' or whatever... This system was simpler but it was easier to use without specially trained personnel and could cover longer distances with the least of fires!
Another type of visual signals used moving flags. I think such a system is still used by the Navy.
The fire signals are probably helped by reflectors in order to get even further. According to History, the famous Lighthouse of Alexandria used such a reflector or even a lens to guide its light as far as possible.
Description of this machine was in the book of Enia the Taktikou,
named Besieging (4th century b.c.). Its description was
rescued by Polivio, but its name was taken by E. Stamati. The picture of the
machine was not rescued from the antiquity, only in
very later period.
In order to transmit the message
it was necessary two mechanisms, which should be synchronized.
In a cylindric container was floated a float with stalk which brought
were determined messages. The container in the base has a pump.
When pump opened, the water was poured out and went down the thing with
the messages. The pump was closed when the bar reached in the no
message that should be transmitted. The moment of opening of the pump, a soldier
rose a torch and the receptor of message with the same appliance opened
his pump. When
the sender's message reached
in desirable hright, he closed the torch and the recipient closed the
pump So the two navigable of the corresponding appliances found in same
level which determined the corresponding message which was transmitted.