10V2T

Sentry 10V2T
Company	Sentry Siren, Inc.
Produced	1973?-2022
Type	Omnidirectional Electromechanical
Sound output	120 dB @ 100 ft
Frequency	60 Hz
Horsepower	10
Voltage	208-230/460 V AC 1 or 3 ph
Preceded by	Sterling Model M
Succeeded by	Sentry 10V1T Sentry 16V1T-B
Documentation	Product sheet

The 10V2T is a dual rotor omnidirectional siren that was produced by Sentry Siren, Inc. over a period of nearly 50 years. Being little more than a vertical 10 hp Sterling Model M at its core with horns attached, it was a mainstay of Sentry's lineup until dwindling sales led to its discontinuation.

The 10V2T's sales dwindled over the years as its price and performance were lacking compared to Sentry's larger dual rotor sirens such as the 15V2T, 16V1T-B, and 20V2T, and the single phase offering was later discontinued, leaving it only available in three phase. This, along with increasing demand for sirens able to run on DC power, ultimately spelled the 10V2T's end. In June 2022, the 10V2T was officially discontinued, being replaced by the smaller 10V1T in September 2022 after a production life of 42 years. Though it is no longer officially produced, it is still available through special order or through Sentry's partners such as W.S. Darley & Co. Many 10V2T sirens are still in service, though this number can be expected to dwindle as the years go by due to their increasing age. These are reliable and trusty sirens nonetheless, and will likely remain in use for many years to come.

History and design

The 10V2T was one of Sentry's earliest original siren designs and was an attempt to improve upon the Sterling Model M, which Sentry had purchased and redesigned in 1973 after Sterling Siren Fire Alarm Company went under. The 10V2T was introduced sometime between 1973 and 1976, when Sentry still operated under the Sterling Siren Fire Alarm Corporation name. The Model M (renamed to the Model M-10 by Sentry) would later be redesigned to share common parts with the 10V2T, and many other sirens would be later introduced after the 10V2T's success, such as the 3V8, 5V, 10V and 20V2T.

10V2T

The 10V2T was the lowest powered dual rotor siren in Sentry's lineup, though it has now been replaced by the 3V8-based 10V1T (not to be confused with the single tone version of this siren which shares the same name) in this respect. Like the 10V, the 10V2T is designed to be effective at both close and long range, through the use of two different horn sizes. The 10V2T comes standard with these horns, though skirts were also available through special order if desired. The horns were originally flat at the end, but this was later changed to slightly pointed horns to help keep debris out. The very earliest prototype 10V2T units used 8 unique rectangular exponential horns attached to each stator port to project the sound. These horns proved to be ineffective or too impractical, and the design was changed to the round horns by the time the siren reached production.

The 10V2T came standard in either single or three phase AC power, with three phase units using a single dual sided 10 hp AC motor, while single phase units used two single sided 7.5 hp AC motors. Single phase units use a centrifugal regenerative brake which slows the rotor down rapidly when the rotor reaches a low enough RPM in order to recharge the motor's capacitor. The 10V2T came standard in 8/16 port dual tone as standard, though 8/8 or 16/16 port single tone were available through special order as the 10V1T (not to be confused with its replacement). The siren was able to reach 120 dB at 100ft as claimed by Sentry.

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 (or motors, if it is a single phase model) 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. Notably, due to single phase units using two motors, the motor cover is significantly taller than three phase units, which makes them easy to differentiate visually. 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 to make installation easier. The 10V2T comes with 16 horns, 8 of which are long while the other 8 are short in length. The horns are staggered in a way where 1 long horn and 1 short horn is facing each immediate and cardinal cardinal direction for maximum long and short range coverage. The 8-port rotor is always located on the bottom, while the 16-port rotor is always on top. The 16-port side has two ports per horn. The horns and both intakes are protected by mesh screens to help keep debris out of the rotors.

10V2T-3S

In the early 1980s, Sentry attempted to create a three-signal variant of the 10V2T. This was designated as the 10V2T-3S, and used a pair of electromagnetic dampers, one in each intake, to create additional signals such as hi-lo or pulse. To fit the dampers, the intakes were extended. As pagers had largely taken over fire departments by the time this siren released, there was little demand for three-signal fire sirens especially due to the increased maintenance these required. The 10V2T-3S was not sold for a long period of time, and was discontinued by the mid 1980s. Approximately 4 are known to still exist. A single example remains active, in Scobey, MT, though it does not use its dampers.

10V2T-SCS

The 10V2T-SCS was one of Sentry's many customized sirens developed for customers with specific needs. The 10V2T-SCS is a variant of the 10V2T that was developed for a methane production plant nearby to Sentry's headquarters which required a siren that was mixed-range and had visual warning built-in. The 10V2T-SCS uses the standard horns on the top 16-port rotor to project the sound far outwards from the plant, while the horns on the bottom 8-port rotor have been replaced with a skirt, which directs the sound from the lower rotor downwards into the plant itself. Since workers in the plant were often required to wear hearing protection onsite, the siren was placed onto a metal frame containing a red flashing beacon, which provides visual notification when the siren activates. Only one of these was ever built, and it is unknown where the siren is and whether or not it is still in service.