Why did Federal stop making the STH-10 siren?

Civil Defense Sirens are Still Made,there are Two Distinguished Types of Civil Defense Sirens....Electronic,and Electromechanical......Electromechanical Sirens use a Spinning Rotor to Force Air through the Ports of a Stator...Generating Sound......Electronic Sirens use Amplifiers,Tone Generators and Large Array's of Speakers to Generate Sound.

The Reason for Discontinuing the STH-10,is indeed because of New Technology....the Modern Equivilent of the STH-10 is the Eclipse 8 which is still made by Federal Signal.

Electromechanical Sirens are still made and Used Today...although Electronic Sirens are Increasing in Popularity.

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The primary reason older-style mechanical sirens, such as the STH-10, XT22, Thunderbolt and so on, have been discontinued are due to a growing desire for outdoor warning sirens that include battery backup, which allows them to continue operating in the event of a power failure. Although an older AC-only siren could be connected to an automatic backup generator to operate during a power failure, the expense of maintaining both a siren and a generator often exceeds the expense of maintaining a new siren with built-in battery backup, especially if a community has multiple siren sites. Communities that still desire mechanical sirens, but wish to switch to a system with battery backup, common choose brands and models such as the FS 2001, FS Eclipse, ASC T-128, Sentry 16V1T-B, and other similar sirens.

Additionally, there is also a desire in many communities to transition to an outdoor siren system that includes the capability of broadcasting voice alerts and messages related to the situation at hand. This is something that mechanical sirens, regardless of age or model, are simply not capable of doing. This is where brands and models such as Whelen, FS Modulator, and ASC i-Force come into play. With no moving parts, electronic sirens are, essentially, amplified loudspeakers with the ability to generate various computer-synthesized warning tones and signals, along with playing pre-recorded or even live voice broadcasts.