These systems (there were three of them)
According to a couple of sources, one of them, X-device, was up and running in
1938 and used in the Polish Campaign...
Johannes Plendl - Wikipedia, the free encyclopedia
When Germany invaded Poland, the X-System was used effectively against military targets, but on a limited basis, due to the few number of planes equipped with the X-Device (X-Gerät, the electronic component of the system carried in the plane.) and the short duration of the campaign.
Based on four beams a "good crew" could drop their bombs within a circle 120 yards in diameter when 70 miles from the beam stations, a circle which increased to 400 yards in diameter when the aircraft was 180 miles from the stations. Because of its complexity the X-device could be used only by specially trained crews. As a result the its use was confined to one precision bombing unit, Kampfgruppe 100.
Purnell's
