An experimental 700 MHz microwave transmitter on the roof of the Westinghouse office building in 1932, part of early research that resulted in microwave relay systems by the 1940s. The 16 inch waves radiated by the vertical dipole "(right)" are focused into a beam by the cylindrical parabolic reflector, which is received by another parabolic antenna a mile away. The microwaves were probably generated by a Barkhausen-Kurz tube, an obsolete vacuum tube oscillator that was one of the few sources of microwaves at that time.