Pontoon bridge in 638. The army of the Umayyad Caliphate built a pontoon bridge over the Bosporus in 717 during the Siege of Constantinople (717–718). The Carolingian army of Charlemagne constructed a portable pontoon bridge of anchored boats bound together and used it to cross the Danube during campaigns against the Avar Khaganate in the 790s. Charlemagne's army built two fortified pontoon bridges across the Elbe in 789 during a campaign against the Slavic Veleti. The German army of Otto the Great employed three pontoon bridges, made from pre-fabricated materials, to rapidly cross the Recknitz river at the Battle on the Raxa
Junk box in large quantities. Cast-off or used electronic equipment make especially good additions to a junk box. What non-hams may see as junk, hams often see as treasure. Hamfests, surplus stores, electronic swapmeets and even dumpster diving are often venues for hams to trade, buy, scrounge, or salvage spare parts and components. Junk boxes can range in size from small cardboard or plastic boxes, to large collections that fill garages and outbuildings. Many hams derive satisfaction from having an especially large junk box full of exotic and hard-to-find components. Others feel that the act of tracking down parts is half the