Sentry 40V2T

**Decibel rating (100ft)** | 127 dB (originally claimed)
 **Type of siren** | Omnidirectional Electromechanical

The **40V2T** is a dual rotor electromechanical siren that is produced by Sentry Siren, Inc. It holds the title as the loudest siren produced by Sentry, as well as one of the loudest omnidirectional sirens ever produced, only beaten by the likes of the H.O.R. Super Sirex.

## 40V2T

The exact date of the 40V2T's introduction is unknown, though documentation exists as early as 1998 using the siren's current design. The 40V2T dethroned the 20VXT as Sentry's loudest siren upon its introduction, with its own unique design. The 40V2T uses different rotors and stators than Sentry's other sirens, which were purpose-built for this siren, and later the 14V which is a 40V2T cut in half.

The 40V2T is unique compared to the rest of Sentry's sirens. The 40V2T uses 10 wide, short horns instead of the usual thin, long horns that the other sirens use. The top row of horns shares 3 ports per horn, while the bottom row shares two. Units built before 1998 used the same horns as the 20VXT, before they were changed to the current design. The horns on these sirens are pointed, to help keep debris out. This idea would be later implemented on all of Sentry's horn designs. The 40V2T comes with these horns as standard, though it can be ordered with skirts if desired. The 40V2T uses a monstrous dual sided 40HP AC motor, which consumes 480V of power. Due to the high power requirements, the 40V2T is only available in three-phase AC. The siren comes standard in 10/15 port dual tone, a unique port combination that has not seen use since the discontinuation of the Decot Red Arrow. The siren is also available in 10/10 port single tone, as the **40V1T**. Only a single 40V1T exists, in Huntsville, AL. The 40V2T was originally rated by Sentry at 127 dB at 100ft, but this was changed for no apparent reason to 131 dB at 100ft despite no design changes. Thus, it is smart to take Sentry's decibel ratings with a grain of salt.

Due to being a vertical omnidirectional siren, its design is quite simple and similar to Sentry's other sirens. The siren itself is held up by a 6-legged mount which is directly attached to the bottom stator, which has a cone on the bottom to project the sound from the intakes better. The motor is in the middle of the siren, between the two rotors. It is protected by a cylindrical motor cover with ventilation holes to protect the motor from the elements. The upper intake on the siren is protected by a large rainshield, that keeps debris and moisture out of the top rotor. An eyebolt is also included as a crane is necessary to lift the very heavy siren into place. The 10-port rotor is always located on the bottom, while the 15-port rotor is always on top. The horns and both intakes are protected by mesh screens to help keep debris out of the rotors.

Due to its size and power requirements, the 40V2T is not as popular as Sentry's other offerings, and it fills a unique niche. This is a fate shared by many oversized sirens such as ASC's T-135 AC/DC. However, it is still able to be found across the United States as it is very loud and cities only need to buy a few of them. While it likely does not live up to Sentry's claims, it is still incredibly powerful. The 40V2T and 15V2T are the last sirens on the US siren market that are sold as dual tone by default.

## 40V2T-B

In 2009, a DC variant of the siren was announced by Sentry, designated as the **40V2T-B**. This siren was planned to use a pair of 8HP 72VDC motors, and would have had a lower sound output due to the sheer size of the rotors making it difficult for the rotors to reach full speed. Due to the immense power requirements, as well as the expense of the huge batteries this siren would have required, the 40V2T-B never made it to production. The siren would often overload its components during testing, and in 2014 it was confirmed by C & K Early Warning Systems that the siren was officially cancelled. Because of this, the 16V1T-B remains as Sentry's largest DC powered siren. At least one prototype unit was built, although it is unknown if it survives today or was rebuilt into a standard 40V2T.

## 40V2T-SC

Another one-off variant of the 40V2T was built for the Holcim cement plant in Portland, CO, which was designated as the **40V2T-SC**. This was a sealed, airtight variant of the 40V2T which was designed to prevent cement dust from getting into the bearings and electrical components of the siren, which would destroy it. The 40V2T-SC used skirts instead of horns, and it, along with the unique 25V2T-SC, were put into service. Only one of these was ever built, and the sole example was eventually removed between 2015 and 2021, with its fate unknown. It was otherwise identical to a standard 40V2T.