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The NSAC N series is a powerful dual tone omnidirectional siren that was produced by the NSAC, (Nizhnyokohama State Alarm Company) a wholly owned government corporation managed by the NISCIDA (Nizhnyokohama State Civil Defense Administration). The N series, though believed to be the Nizhnyokohaman government's response to the ACA Cyclone, was a siren nearly as powerful as the Cyclone. At the time of its release, it had established itself as one of several most popular omnidirectional sirens ever produced in the nation of Nizhnyokohama. It still continues to this day to compete with much newer sirens like Nizhnyokohama's own Daisugrad P-128 and S-135. It was the loudest omnidirectional siren the NSAC offered from its release in 1969 until the 1989 introduction of the OM-130. The Mark II N series, along with the RM-50, had matched production runs, both being produced for nearly 14 years.
History[]
Backstory[]
Since the start of the Détente between the US and USSR in 1967, friendly relations with Slavic nations have been a top priority for the US. In Nizhnyokohama, the United States prioritized preserving the nation's internal political order, reviving its economy, and escalating its militarization. Under these new policies, the United states—as well as Western Bloc countries such as Britain, Canada, West Germany, and France—started shipping supplies to the country, this especially included a set of civil defense sirens that were installed as a brand-new nationwide siren system. The majority of sirens ended up being from Britain and France whilst the American-made sirens specified in the initial order by the government consisted of 24 Federal Sign and Signal sirens and 70 Alerting Communicators of America sirens manufactured in Milwaukee, Wisconsin. The new system replaced a fraction of a much older siren system which consisted of typically unreliable to decent sirens manufactured in machine shops across the nation. However one particular model was standardized by the government that was called the Type 522. Most that were manufactured used a weatherproof motor, which mitigated the necessity for any weather protection but this made the siren costly. Ultimately, the government resorted to cut down costs by switching to more cheaper and reliable motors and as a result started using a motor setup on later Type 522 sirens that had a noticeable lack of weather protection for the motor, so to compensate for protection against the elements, the siren used either a steel or aluminum barrel housing over it. Eventually, NISCIDA became determined to address the reliability issues discovered in the Type 522 model that they had previously standardized in addition to seeking to create a new siren because of pressure from some regions that were refusing to accept the influx of surplus and supplies in general from the States during détente. This took the form of creating a new, standardized dual tone siren model that drew inspiration from one particular American model while also being just as dependable as the American sirens being imported into the country. This new line of sirens would use more reliable motors in a huge contrast to the earlier warning siren system. Despite this, the independent siren manufacturers already solved these problems almost a decade before via either using the expensive weatherproofed motors or resorting to the cheaper motors and putting a protective housing over the siren, which concealed the weather-prone motor.
Development[]
NISCIDA eventually went to the United States to study the design of sirens at the Federal Sign and Signal manufacturing facility in Chicago, Illinois and observed the operations of dozens of U.S. manufacturers. The specifically studied the design of Federal Signal's 500 SH-TT siren and SD-10. With the knowledge and designs gained from the trip, Agent Dimitri Ford of the NISCIDA started to sketch designs for what would become the N series. One particular design, which ended up being chosen by the NSAC for manufacturing, was heavily reminiscent of the Cyclone siren model manufactured and designed by the American company Alerting Communicators of America.
The design of the N series rotor, note the dual intake design element. The arrow shows the actual direction of rotation.
In this design, the chopper consists of a stator with miniature angled horns on the port openings and a "double intake" rotor design, both of which are in fact inspired directly by Federal's 500 SH-TT; a version of this design was also used in the NSAC Y series, a multipurpose siren designed by the NSAC mainly for use at fire stations and as a curfew siren. The rotor design optimized airflow, but at the same time induced significant drag, necessitating the usage of a 20hp motor. This design debuted in 1969 as the N-20 siren and was manufactured by the NSAC. The NSAC later released the N-50 model by 1972 which was identical in all aspects but the only exception was it had a 50hp motor instead of a 20hp one, resulting in a snappier windup. This version of the line was dubbed Mark 1 (MKI) and had a 14 year production span from 1969 to 1983. The government this time was able to make a steady profit over the siren due to the usage of cheaper components such as the motors, and the materials used for the chopper assembly.
Later design revisions[]
In 1971, the NSAC and the government were experimenting with making original designs to distance the N series from the Cyclone. One of these designs had a slightly re-designed top cover, had the top row of ports being straightened out and the bottom row of ports angled downwards, as to direct the low tone outwards for maximum range while projecting the high tone downwards to the immediate area. It also had a ring placed around the bottom of the stator to direct the sound outwards more smoothly.
The updated design was dubbed as the Mark II and it entered production in 1973. The Mark II ditched the conical stator and reverted to the parallel stator used on the Mark I design, projecting both the high tone and low tone outwards. This was further assisted by the top cover of the siren being changed out for a housing reminiscent of a Federal SD-10 shroud that covered the entire siren. However it had design tweaks in order to to better distinguish it from the SD-10. As such the housing appeared slightly shorter with its curved shroud pieces extending further than the vanes and defection band.
The new design also omitted the older single unit intake/mounting pedestal. This time however, rather than being welded like the Mark I model, the separate mounting pedestal and intake were attached using specialized hardware. Allen bolts were used to connect the stator to the intake, and setscrews were used to secure the intake to the stand. This configuration made it possible to attach custom mounting components onto the siren, giving more freedom for mounting the siren effectively. It could also be specified with a redesigned single piece intake/mounting pedestal, being little more than a + shape with the same hardware being used to attach it to the siren and/or the siren mount. At this time, NSAC unveiled the RM-50, a rotating siren which also reused the rotor and stator from the Mark 2 version of the N series. Both the Mark II and the RM-50 sirens were produced for another 14 years from 1977 until 1991.
Models[]
20-MKI[]
The 20-MKI, also known as the MKI-N52, N20-50 MKI, N20-MKI, or simply N-20, is the first siren of the N series. The siren uses a 20HP AC motor rated for 50hz and was able to reach 115db at 100ft, just 5 decibels shy of the ACA Cyclone 120. As the motor spins at 2350 rpm, the siren comes standard in 10/15 port dual tone, a unique port combination at the time that hasn't seen use since the discontinuation of the Decot Red Arrow.
What is especially unique is that the 10/15 rotor in the N-20–as well as subsequent members of the N series–used a unique "dual intake" design which is surprisingly similar to the intake rotor designs of the Federal Signal 500-SHTT, ACA Cyclone, or P-50. This design maximized airflow to improve performance, but also increased drag, necessitating the use of the 20HP motor. The Y series–which is a close relative of the N series–also had an optional dual intake design and a complementing 15 horsepower motor–5 horsepower less than the N-20–though the Y series siren typically used a conventional single intake design and a 7.5 horsepower motor.
Despite this, the NSAC would experiment with using a ring around the stator and a redesigned housing in an attempt to improve the performance of the siren further, but this was ultimately scrapped in favor of a unique housing in 1973. The new shroud is of an all-fiberglass casting, which helped to prevent the siren from corroding from the elements. The shroud is also slightly reminiscent of the shroud on Federal's SD-10 model; However it was more of an original design so as to distance the N20 from the SD-10, boasting instead four much smaller "vanes" inside of two curved shroud pieces that were unusually elongated. The deflection band surrounding the stator was also widened significantly, leaving a gap that is now sufficiently wide to pressurize the sound and increase the siren's volume. However, this didn't exactly help to project the sound, and if the deflection band is removed, the sound will be much louder anyway. The finishing touch was the option for the housing to be pointed on top in a manner similar to the Decot Red Arrow Series, however this usually meant an eyebolt delete although some examples with pointed tops were fitted with eyebolts regardless.
MKI-N62[]
The MKI-N62, also known as the Model 20-60 or N20-60, is a variant of the 20-MKI that uses a 20HP 60hz AC motor coupled to a 8/12 port dual tone rotor and stator instead of a 10/15 port rotor. Unlike the regular 20-MKI, which has a 50hz motor that spins at 2350 rpm, the motor found in the Model 20-60 spins at around 3450 rpm which makes the siren comparable in pitch to its 50 hz sibling.
Sales of the Model 20-60 within the regions of Nizhnyokohama with 60hz mains power were as comparable as the N20-50, which equally sold well in parts of the country that had 50 hz mains. Like the other members of the N series, the Model 20-60 was designed and issued by the government for use as a civil defense siren, although it easily doubled as a fire and a weather siren by the time the need for dual tone sirens had ended with the end of the Cold War. The MKI-N62 became popular alongside its 50hz brother and gradually outsold both the N50-50 and N50-60 significantly.
MKI-N55[]
The MKI-N55, often known as the N50-50 MKI, N50-MKI, or simply N-50, is a more powerful version of the Model 20-50. Like the Model 20-50, it uses a 10/15 port dual tone rotor and stator, and is visually identical to the Model 20-50. However, the MKI-N55 uses a 50HP AC motor that spins at the same rpm as the motor in the 20-MKI, causing shortened windups distinctive to the siren.
The Model 50-50 also received an update in 1973 which carried over the same unique fiberglass shroud from the N20. However, unlike the N20 which had the option for the housing to be pointed on top, the pointed top was standard on the N-50. Although unintentional, this helps to it set it apart from the redesigned N20 apart from the obviously quick windup. Sales of the N50-50 were undetermined, but it did see effectiveness outside of civil defense uses.
MKI-N65[]
The MKI-N65, often known as the Model 50-60 or just the N50-60, is an 8/12 port variant of the MKI-N55 with a 50HP 60hz AC motor. The Model 50-60's motor–which is rated for 60 hz–spins at 3450 rpm as opposed to the N20's motor which is rated for 50hz and spins at 2350 rpm respectively, hence the pitch of the N50-60 could be comparable to that of the N50-50 in a manner similar to the 50 and 60 hz versions of the N-20.
Sales of the N50-60 within the regions of Nizhnyokohama with 60hz mains power were less popular than the MKI-N62. As it had the same range and volume as the MKI-N62, it was originally designed as a multipurpose siren mainly for use as a standard civil defense siren along the other sirens in the N series, however the N50-60 mainly ended up being used as a fire or curfew siren like its 50hz sister due to the faster windup. It also doubled as a standard civil defense and weather siren when necessary.
20-MKII[]
The 20-MKII was the successor to the 20-MKI, being introduced in 1983. It is also known as simply the N-20 like the MKI-N52, but the 20-MKII is also referred to as the MKII-N52, N20-50 MKII, or N20-MKII. The MKII-N52 (or the 20-MKII) was a refined version of the 20-MKI, and the intake and housing were redesigned. The siren also carried over the fiberglass shroud that was introduced for the MKI-N52 in 1973, albeit resized to fit over the siren assembly; the newer design omitted the defection band from the shroud entirely, with the option to replace the entire shroud with a fiberglass motor housing instead. This motor cover also had a lip added to the bottom of that improved sound projection. Having a drastically larger decibel rating of 125db at 100ft, the 20-MKII offered superior range thanks to the aforementioned changes and thus beats the 20-MKI by only 10 decibels. The same year it was introduced, NSAC also introduced the RM-50, which was essentially a rotating N series siren, using the rotor, motor and stator from the MKII-N52.
There was also a 50hp version of the 20-MKII, however it was instead treated as a part of the Y-series. Despite being based on the 20-MKII, the MKII-Y55 was essentially treated as a separate siren from the N series and designed exclusively for use as a fire or curfew siren since sales of the previous MKI-N55 within Nizhnyokohama were overall less popular than the MKI-N52. As a result, the siren completely lacks a shroud and is turned upside down with an intake and a rain shield on top to prevent moisture and debris from entering the rotor.
MKII-N62[]
The MKII-N62, also referred to as the Model 20-60 or N20-60, is a variant of the NKII-N52 that uses a 20HP 60Hz AC motor coupled to an 8/12 port dual tone rotor and stator rather than a 10/15 port rotor and stator. The Model 20-60 has a motor that spins at about 3450 rpm, making the siren's pitch comparable to that of its 50 hz sibling. This is unlike the MKII-N52 which has a 50 hz motor that spins at 2350 rpm.