For a decade France maintained a mixture of optical telegraph and electrical telegraph systems on its network. The Foy-Breguet system ensured that operators could easily be transferred from the optical to the electric systems, although many optical operators (semaphorists) declined to become telegraphists when their lines were updated. The semaphorists were largely rural workers on isolated stations used to taking on the responsibilities of carrying out mechanical repairs by themselves. After all, if the equipment broke down, they no longer had the means to call for assistance. Telegraphists were located in offices with management and service personnel on hand. They were forbidden from attempting any kind of repair and had a more paperwork intensive job. Despite its advantages in the French context, the uniqueness of the French system eventually led to its decline. During the 1850s, as international telegraph traffic grew, having different telegraph systems in different countries became increasingly problematic. Direct connections were not possible and operators had to be employed to recode messages crossing borders. The code that was later to become known as International Morse Code was adopted in several countries. It was first used on Hamburg railways and was devised by Friedrich Clemens Gerke. This code was a heavily modified version of the original American Morse code and was known as the Hamburg code or Gerke code. Gerke's code was adopted in 1851 by the German-Austrian Telegraph Union which represented many central European countries. In 1855, France also adopted the code and replaced the Foy–Breguet telegraph equipment with the Morse system.