PHOTO-ELECTRIC "ARC EXTINGUISHER"
Photo Electric Cells
The photo-electric "arc extinguisher" ---somewhat resembling a machine gun--- is mounted on the wall behind the base insulator supporting the 831-ft. WLW vertical radiator antenna tower.
"Aimed" through the lightning protective gap, it picks up the light of any discharge and prevents power drainage by momentarily interrupting the plate voltage to the transmitter.
Without this device, an arc across the gap would carry off from the antenna virtually all of WLW's 500,000 watts power---enough electrical energy to fill the residential lighting requirements of a city of 150,000 population.
The photronic cell and its associated relays are mounted in a double metal box which carefully shields them from the strong radio frequency fields at the base of the antenna.
The photronic cell is mounted at the end of the "barrel"
or light tube. The power relay operates directly on the transmitter
control circuits and also operates indicators in the transmitter building.
Original Caption by Science Service