Federal Signal Model A

The **Model A** is a small industrial electric siren produced by the Federal Signal Corporation, and is the oldest siren still produced by the company, as well as one of the oldest siren designs currently still in production. This siren is intended for use in industrial areas, indoor use, and short range outdoor warnings. The Model A shares this purpose with the heavier duty Model L in Federal Signal's lineup.

Due to its small size, the Model A is popular both with industrial sites requiring a small siren, as well as with siren enthusiasts who commonly buy these sirens due to the ease of restoring and operating them. Model As can also be commonly found on drawbridges, warning when the bridge is raising. The Model A has stood the test of time as a reliable, cheap siren that gets the job done wherever it is installed. Its closest competitor is the Sentry F-2, as well as Federal's own Model L.

## History and Design

The Model A was first introduced in 1918 by the Federal Electric Company as the Type A, and was released alongside the larger dual rotor Type Mach. B. The Type A was designed for short range use compared to the Type B, able to be mounted on nearly any surface. The siren became popular as an industrial warning siren, as well as a fire siren for rural communities. The Model A is simple in design, being a small single rotor electric siren. The siren uses a small 6-port aluminum rotor and stator, driven by a 1/2HP AC/DC universal motor running at 120V AC/DC. The motor runs at a high RPM, with the siren peaking at 1060HZ. The stator ports have finger guards included, though early Type A models lacked these guards. A 220V alternative of the Model A was available a few years after the Model A was introduced, named the Model J. The Model A is rated at 103 dB at 100ft.

By default, the Model A comes with a metal stand which attaches to the motor cover through two swivel mounts, which allows the siren to be aimed vertically wherever is required. These mounts are secured by nuts to keep them in place. The stand includes holes for mounting on a wall, floor or ceiling. The design of the Model A itself has changed over the years, with the earliest models using sleeve bearings with external oil sumps attached to the motor cover, and the siren lacked finger guards on the stator ports. This was changed early on to include the finger guards, and the sleeve bearings were replaced with different bearings which resulted in the oil sumps being removed. Between 1918 and 1970, the Model A used a large conical skirt to project the sound from the ports, as well as a smaller conical intake.

In 1970, the siren received a redesign, with the intake being enlarged and a flanged outer skirt borrowed from the Model D and Model L replacing the conical skirt. Little has changed since then, with the only major change being the metal tags being switched over to stickers on newer units to save on costs. The tag placement has also varied, originally being mounted on the skirt before being moved to the motor cover, where it remains today. Like the Model L, the Model A comes painted red from the factory. The Model A was optionally available with a corrosion-resistant brass housing for marine use, as the salty ocean air would quickly corrode a regular siren.

### Variants

The Model A was available with a different design that was produced for a short time. These ran on 6V, on either AC or DC power, and were likely operated off of batteries. These were likely meant for vehicular use such as on fire engines or other emergency vehicles, as Federal had not created the Q-Siren or its other popular vehicular sirens yet. The siren has larger conical intake, smaller flared projector similar to a Sterling Type F, and completely lacks a swivel stand. The siren has a mount designed to be attached to the front of a vehicle, and has a cylindrical motor cover. It does not appear that these were produced beyond 1948, as all known units are Federal Electric branded.

    The Model A was also available in other models, such as the **Model A-5**, which is a 5-port variant of the siren which peaks at a lower pitch. These are essentially Model Ds with a 5-port rotor and stator replacing the usual 8-port rotor and stator. Due to using a larger rotor with long vanes, these are louder than standard Model As.
A vertically mounted variant of the Model A was also produced, in the form of the **Model AV**. The Model AV uses a small pipe attached to the intake which forms the stand, with the siren facing downwards. These sirens were designed to be mounted on top of traffic signals for street clearing purposes. No Model AVs are known to still exist, although there may be some that have not been found.

A smaller variant of the siren was also produced in the form of the **Model B-9**, which is an indoor variant of the Model A. The Model B-9 was mainly designed for indoor use in quieter environments, such as office buildings and similar installations, and was recommended by Federal to have one of these sirens on every floor of a building. The Model B-9 lacks an intake cone, instead using a metal grille, and uses a much smaller skirt, and uses a simplistic non-swivel static mount attached to the motor cover. The Model B-9 is much more portable than a standard Model A, and its reduced performance makes it more suitable for its purpose. The Model B-9 was discontinued by the Federal Signal era.

The Model A was available as the **Triple-A**, which consists three Model A units attached to a common frame facing in 120 degree intervals for uniform coverage. The siren was advertised for short range fire siren use, and could come with either a stand with the sirens on top, or with a platform with the sirens mounted below it on a pole which helps protect the sirens from the elements. Each siren operates at a different pitch due to their universal motors, creating three distinct tones at once to help distinguish the sirens over ambient noise. Very few Triple-As remain in existence today.