Xerxes' Pontoon Bridges Xerxes' Pontoon Bridges Xerxes' Pontoon Bridges were constructed in 480 BC during the second Persian invasion of Greece upon the order of Xerxes I of Persia for the purpose of Xerxes’ army to traverse the Hellespont (the present day Dardanelles) from Asia into Thrace, then also controlled by Persia (in the European part of modern Turkey). The bridges were described by the ancient Greek historian Herodotus in his "Histories", but little other evidence confirms Herodotus' story in this respect. Most modern historians accept the building of the bridges as such, but practically all details related by Herodotus are subject to
Coaxial cable other types of radio transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference. Coaxial cable conducts electrical signal using an inner conductor (usually a solid copper, stranded copper or copper plated steel wire) surrounded by an insulating layer and all enclosed by a shield,