Pennsylvania Railroad EMD F-Unit 9830 leads a freight train near Mackinaw City, in 1950.  The double rail system on the top of the locomotives were antennas for the inductive two-way radio system.  The radios in the locomotives transmitted to line-side inductive receivers.  The PRR stayed with the system for several years, even after other railroads switched to more traditional two-way radios. 

[Doug Leffler Collection]