The Federal Signal Thunderbolt siren is one of the most famous "older siren" in the history of sirens. The Thunderbolt siren consists of three major parts: the blower, rotator and siren chopper. The blower, which is made up of a motor-driven Roots-type supercharger, supplies the big volume of air for the siren head, It is housed inside a large rectangular box typically found at the base of the siren head. The rotator is a motor-driven gear unit which rotates the directional horn/projector to direct the sound where the horn is at. The chopper is located in the cylindrical housing that the horn/projector attaches to at the top of the siren.
The Federal Signal Thunderbolt was the siren of choice by many Civil Defense authorities and emergency management agencies from the early 1950s through the late 1970s. Since the Thunderbolt was introduced in 1952 during the beginning of Cold War tensions as primarily an attack warning siren the high volume during all phases of the attack signal was stressed in advertising the siren by Federal Signal. One of the most distinguishing features of the Thunderbolt siren's sound is the dramatic volume in the down-pitch phase of the signal. It's usually this part of the signal that carries the farthest and is the most "attention-getting."
- Model 1000, a single-tone siren capable of two signals (alert and attack). (126dB at 100 feet)
- Model 1000T, a dual-tone version of the 1000.
- Model 1003, a dual-tone version with the added capability of producing a fire signal with solenoid valves.