Captain of PS "Stadt Zürich" giving orders by speaking tube.
Heinz Baumann
CC BY-SA 4.0
ETH-Bibliothek Zürich, Bildarchiv / Fotograf: Baumann, Heinz / Com_Ex-BA01-0004-0008 / CC BY-SA 4.0 / <a rel="nofollow" class="external free" href="https://doi.org/10.3932/ethz-a-001088212">http://doi.org/10.3932/ethz-a-001088212</a>