7V8

7V8
Sentry 7V8
Company	Sentry Siren, Inc.
Produced	2000-Present
Type	Omnidirectional Electromechanical
Sound output	112 dB @ 100 ft (7V8) 121 dB @ 100 ft (7V8-B (claimed))
Horsepower	7.5 or 8 hp
Voltage	208-230/460 V 1 or 3 ph 72 V DC
Preceded by	Sentry 5V

The 7V8 is an omnidirectional siren produced by Sentry Siren, Inc. It is the midrange single-rotor siren in Sentry's current lineup, improving upon and replacing the 5V for this purpose.

History and design

7V8

The 7V8 was introduced in the year 2000, alongside the 16V1T-B. The 7V8 was designed to replace the 5V, which lacked any sort of amplification for its sound and became redundant. The 7V8 reaches the same sound output as the 5V, at 112 dB at 100 ft, but the addition of horns allows the sound to be projected further. The 7V8 comes standard with an 8-port single-tone rotor and stator driven by a 7.5 hp AC motor, with each stator port having a horn attached. Like most of Sentry's sirens, the rotor and stator are borrowed from the Sterling Model M.

The 7V8 comes with horns as standard, though it can be ordered with a skirt. The horns on the 7V8 were originally flat at the end, but these were later replaced with pointed horns to keep snow and debris out. These horns are very similar to those used on the 3V8-H, but larger in size due to the 7V8's larger rotor. The 7V8 can also be ordered with the long horns used on the Sentry 10V. The 7V8 is made out of steel as standard, though Sentry also offers the siren in corrosion-resistant stainless steel if desired.

Like all of Sentry's single-rotor sirens, the siren's design is very basic, with the rotor and stator being attached to a 6-legged mount that has a cone to project the sound from the intake outwards. The motor itself is placed inside a weatherproof housing above the siren. This simple design allows the siren to be both cheap and easy to maintain. The 7V8 is available in either single or 3 ph AC, with 1 ph units using a centrifugal regenerative brake which slows the rotor down rapidly when the rotor reaches a low enough RPM to recharge the motor's capacitor. The siren can reach 112 dB at 100 ft according to Sentry.

7V8-B

In 2002, a DC-powered battery backup-capable version of the 7V8 was released, designated the 7V8-B. The 7V8-B uses an 8 hp 72 V DC motor instead of the 7.5 hp AC motor of the standard 7V8, which allows the siren to run on battery backup if AC power is lost. The siren is rated to run approximately 30 minutes after AC power is lost before the batteries run out of power. The 7V8-B is otherwise entirely identical to the standard 7V8 in both appearance and performance, and the only way to differentiate the two is the 7V8's battery enclosure, tag, and non-linear windup. It is one of four mechanical sirens made by Sentry that have DC battery backup variants, the rest being the 3V8-H-B, 14V-B and 16V1T-B.