jancancook
Posts : 1136
Join date : 2011-01-02
 |  Subject: Ancient systems  Fri Mar 25, 2011 3:25 pm | |
| Greek hydraulic semaphore systems were used as early as the 4th century BCE. The hydraulic semaphores, which worked with water filled vessels and visual signals, functioned as optical telegraphs. However, they could only utilize a very limited range of pre-determined messages, and as with all such optical telegraphs could only be deployed during good visibility conditions.[2] orchid fertilizerget more web traffic | |
|
