Tensioning assembly of the overhead wires in Graz Hbf. Both wires of
the catenary are tensioned by the same weight; the reel mechanism
increases the pulling force. The weight can go up and down, so the
wires are at the same mechanical tension if they contract and expand 
at different temperatures. On a winter day, the weight would be higher
up because the wires are shorter. 2002-09-05.
<p>
photo: <a href="mailto:tbk@uncia.de">tobias b köhler</a>