508-128

Model 508-128
A Model 508-128 in Hartford, OH. Photo taken by Fumikiri06.
Company	Federal Signal Corporation
Produced	2011-present
Type	Rotational Electromechanical
Sound output	128 dB @ 100 ft
Horsepower	6.5 hp
Voltage	48 V DC
Preceded by	Federal Signal 2001-130
Documentation	Manual Product sheet

Model 508-128, also commonly shortened to Model 508, is a rotating DC electromechanical siren produced by Federal Signal and is the newest mechanical siren in their lineup. Originally intended for use in areas near nuclear plants, the 508-128 has also enjoyed popularity as a severe weather siren. It is sold alongside the 2001-130 and the Model ECLIPSE as Federal Signal's main outdoor warning siren offerings.

History and Design

The Model 508-128's chopper and horn throats are visible from the front.

Model 508-128 was introduced in 2011 as a refined version of the Equinox. The Equinox had several issues, including the chopper sticking out into the rear housing which reduced airflow and harmed sound output, causing the siren's performance to fall flat. The 508-128 fixed this problem by completely redesigning the projector. The chopper now faces forwards with the motor being located in the rear housing, and a significantly enlarged projector and intake lets the chopper have more than enough air. This gives it significantly better performance than the Equinox. The 508-128 is designed to compete with ASC's T-128, although the T-128 performs better than the 508-128 by nearly 2 decibels.

A 508-128 rotor (top) and a Tempest rotor (below). The 508-128's rotor is very heavily derived from the Tempest's rotor and is sourced from the same casting company.

The internals of the 508-128, with the collector ring assembly highlighted by the arrow. This is the same assembly used in the 2001 series and the Thunderbolt.

The 508-128 has a distinctive design, reusing several parts from the 2001-130. The direct-drive rotator is identical to the rotator used on the 2001-130, rotating the head at 3 rpm. The collector ring assembly is also identical, being reused from the 2001-130 and the Thunderbolt. The housing itself has been enlarged with a pentagonal shape to add additional support for the projector. The fiberglass projector has also been redesigned, using a different "sunflower" shape. Like the 2001-130, 8 horns are attached to the eight stator ports, which directs the sound forwards and out the front of the siren. However, unlike the 2001-130, the horns are significantly larger, and all merge into one single large projector. The intake is very large, and slightly conical in shape to help direct sound forwards while also maximizing airflow. The rotor itself, which is heavily derived from ASC's Tempest rotors, also uses an integral conical intake with directional vanes. The 508-128 is most efficient running counterclockwise. The rotor and stator themselves are borrowed from the Eclipse-8, just like the Equinox. The siren is driven by a 6.5 hp DC motor, which allows for battery backup capabilities. All of this allows the siren to reach 128 dB at 100 ft.

Being such a new siren, the 508-128 is not as common as other modern sirens such as the T-128 or 2001-130 as they have had more time to sell units, however the 508-128 is quickly becoming more popular as it is an effective siren with great range and power and is commonly being installed to replace older systems or as an addition to existing systems. The siren does have some issues, namely numerous rotator failures and early units suffering catastrophic housing failure from the projector being too heavy and damaging the housing. However, these have likely been resolved since. These sirens also tend to suffer from quality control issues. Today, the 508-128 is a solid option for cities looking to invest in a Federal Signal system, though many cities opt for the cheaper Equinox.