Thunderbolt
The Thunderbolt siren was a supercharged electromechanical siren produced by Federal Electric, later Federal Sign & Signal and Federal Signal.
Thunderbolt 1000
Thunderbolt 1000T
Thunderbolt 1003
The Thunderbolt 1003 is a supercharged siren that is part of the Thunderbolt siren series, the Thunderbolt 1003 uses two solenoids that are attached to the upper portion of the siren, these solenoids are used to create the Hi-Lo signal, which is an alternation between lower and higher frequencies from the siren's chopper.