Do STI Stopper covers prevent legitimate emergency use?

No. STI Stopper II and Stopper III covers are designed to deter vandalism and accidental activation, not block legitimate emergency use. The cover opens easily by any user who needs to activate the fire pull station, sound an alarm, or make an emergency call. The tamper horn on Stopper III provides audible deterrence but does not prevent emergency operation.

Will Stopper III's tamper horn go off every time someone lifts it?

Yes — that's the design intent. The piezo horn sounds at 95 dB for approximately 15-30 seconds when the cover is lifted, providing audible warning that the protected device is being accessed. For legitimate emergency use, the horn will sound as the user triggers the fire pull station or emergency button — which is acceptable because the fire alarm or emergency call will follow immediately.

Are STI covers ADA compliant for emergency communication?

STI emergency call-box covers are specifically engineered for ADA Section 4.31 compliance — integrated signage with raised 'EMERGENCY' text, high-contrast visual markings, and tactile edges meet accessible-communication requirements. For fire alarm covers, ADA compliance applies to the mounting height and operable-surface requirements of the pull station itself, not the cover.

Can I install STI covers over any brand of fire pull station?

Most STI covers use a universal mounting system that fits the majority of North American fire pull station form factors (Simplex, Notifier, Honeywell Silent Knight, Edwards EST, Fire-Lite, Gamewell FCI). For specific models that don't fit the universal mount, STI ships brand-specific mounting kits. Consult our engineers with the specific pull station model before ordering if you're uncertain.

Do STI weatherproof cabinets need additional weatherproofing?

STI NEMA 4X weatherproof cabinets are sealed enclosures that don't require additional weatherproofing for typical outdoor deployment. The NEMA 4X rating covers water jet ingress, dust, and corrosion resistance. For extreme environments (coastal salt spray, industrial chemical exposure, Arctic temperatures), verify the specific enclosure rating meets site requirements.

What's the difference between Stopper II and Stopper III?

Stopper II is the basic clear polycarbonate cover without tamper horn — it provides physical protection and visual deterrence at a lower price point. Stopper III adds an integrated 95 dB piezo tamper-warning horn that sounds when the cover is lifted — providing active audible deterrence that's particularly effective in K-12 schools and public commercial buildings where false alarm rates matter.

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STI EM362408

STI EM362408 Metal Protective Cabinet Lock/Strike
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STI EF181610-W2

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STI STI-6602-CY

STI 6602CY Replacement Horn

Custom yellow replacement horn for STI-13000 stop button systems
- Wired 9VDC operation matches STI-13000 series specifications
- Color-matched yellow horn component for visual alert applications
- Direct compatibility with STI-13000 universal stop button assemblies
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STI STI-6520-C-FR

STI 6520 Identification Reader Cover - STI-6520-C-FR

Clear polycarbonate hinged cover sized for biometric fingerprint readers and integrated keypads in access control installations
- Clear polycarbonate shell keeps biometric and keypad readers visible and operational.
- Rated –40°F to 250°F, supporting reliable outdoor and cold-climate deployments.
- Includes mounting screws and gasket; installs on existing anchor points, no special tools.
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STI STI-4100

STI STI-4100 Break Glass Stopper Large

Large-format break glass stopper designed to protect emergency keys and documents while keeping them visible and accessible during a life-safety event
- Large-format stopper fits keyboxes requiring a 100mm × 111mm aperture.
- Protects keys from unauthorized access while enabling instant break-glass override.
- Supplied with a complete fixing kit for direct mounting to wall or door frame.
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STI STI-15020ML

STI Euro Stopper® Flush Mount Multi Kit with - STI-15020ML

Protective cover retrofit assembly for break glass fire alarm call points designed to prevent accidental or malicious false alarms without blocking
- Retrofits over existing break glass call points with four-point fixing — no device modification.
- Integral 96 dB sounder runs on 24VDC, integrates directly into existing fire alarm circuits.
- Polycarbonate housing glows in the dark and operates reliably from -40°F to 120°F.
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STI STI-1286

STI STI-1286 Strike Backplate for STI-9711/STI-9714

Replacement strike backplate engineered for STI-9711 and STI-9714 electric lock systems
- Purpose-built for STI-9711 and STI-9714 strikes—no cross-model guesswork.
- Operates at 9VDC, integrating directly with existing compatible power supplies.
- Restores precise strike alignment in door frames without specialized tooling.
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STI STI-1283

STI Backplate for and STI-1221D - STI-1283

Replacement backplate assembly for STI electronic strike models operating at 9VDC
- Drop-in replacement for STI-1210C/D and STI-1221C/D strikes at 9VDC — no rewiring required.
- Four-point masonry mount uses 7mm drill holes with included hardware for concrete, brick, or metal frames.
- Four cable gasket ports (gaskets sold separately) seal conduit entries against moisture and vermin ingress.
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STI STI-1229HTR240-WD

STI Stopper® Dome Heated Enclosure for - STI-1229HTR240-WD

NEMA 4X rated heated dome enclosure designed to protect strobe-only warning appliances in outdoor and harsh environmental conditions
- NEMA 4X rated dome shields outdoor strobes from water, dust, and corrosion.
- 240V heating element maintains optics in cold or harsh environmental conditions.
- Compatible with AMSECO SL24W-153075 strobe series; centered lens preserves signal throw.
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STI STI-1229HTR240

STI Stopper® Dome Heated Enclosure for Strobe - STI-1229HTR240

NEMA 4X heated dome enclosure designed to protect strobe-only warning appliances in outdoor and harsh environments
- NEMA 4X rating provides dust-tight, spray-tight, corrosion-resistant outdoor protection.
- Clear dome preserves strobe light transmission while shielding lens from UV and weather.
- Six pre-drilled mounting holes with included hardware simplify installation to backboxes.
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About STI

Safety Technology International, Inc. (STI), headquartered in Waterford, Michigan since 1977, manufactures the industry's broadest catalog of protective covers and shields for life-safety and security devices. STI covers are specified wherever vandalism, accidental activation, weather exposure, or tamper risk threatens device reliability — with the Stopper II and Stopper III lines alone covering virtually every fire alarm pull station and manual call point in the North American commercial market.

The product catalog is organized around five primary application areas: fire alarm protection (Stopper II without horn, Stopper III with integrated tamper-warning horn, specialized covers for duct detectors and smoke detectors), HVAC and thermostat protection (clear universal covers preventing occupant adjustment), security device protection (exit-button shields, emergency call-box enclosures, camera anti-vandalism cages), outdoor weatherproofing (weatherproof cabinet enclosures for outdoor-mounted devices), and ADA-compliant wayfinding (emergency call covers with integrated visual signage meeting ADA Section 4.31 requirements).

STI covers are engineered from thermoformed clear polycarbonate — the material used in ballistic shields and riot helmets — which provides impact resistance 250x greater than standard glass or acrylic while remaining fully transparent for visibility. Tamper-warning horn models add a loud piezo alarm that sounds when the cover is lifted, deterring vandalism attempts and alerting facility operators to tampering events.

Where STI Fits

STI fits every deployment where life-safety or security devices must remain operational but are at risk of vandalism, accidental activation, or weather damage. Primary applications include K-12 schools (Stopper III with tamper horn on every fire pull station to prevent false alarms), healthcare facilities (thermostat covers in psychiatric and pediatric units, emergency call covers throughout corridors), commercial office buildings (exit-button shields to prevent accidental door triggers), parking garages and transit (emergency call-box covers with ADA signage), outdoor installations (weatherproof cabinets for fire panels and access control), and retail/hospitality (thermostat covers preventing customer adjustment). STI is specified by fire protection consultants and life-safety integrators for virtually every institutional and commercial project in the North American market.

Why Choose STI

Industry-Standard Vandalism Prevention

Stopper II and Stopper III are the default specification for fire alarm pull station protection in K-12, healthcare, and public commercial buildings.

Tamper-Warning Horn Deterrence

Stopper III's integrated piezo tamper horn sounds at 95 dB when the cover is lifted — actively deters vandalism and alerts operators to attempted tampering.

Ballistic-Grade Polycarbonate

Thermoformed polycarbonate delivers 250x the impact resistance of glass or acrylic while remaining fully transparent for visibility and legitimate emergency use.

ADA-Compliant Emergency Signage

Emergency call-box covers ship with integrated ADA Section 4.31 compliant signage — raised text, high contrast, and required visual indicators.

STI

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STI products

About STI

STI Product Families

Featured STI Products

Where STI Fits

Why Choose STI

Industry-Standard Vandalism Prevention

Tamper-Warning Horn Deterrence

Ballistic-Grade Polycarbonate

ADA-Compliant Emergency Signage

STI Technology Stack

Thermoformed Polycarbonate

Stopper III Tamper Horn

Universal Mounting System

ADA Section 4.31 Compliance

NEMA 4X Weatherproof Enclosures

Low-Profile Mounting Depth

Typical STI Deployments

K-12 School District

Hospital Psychiatric Unit

Parking Garage Emergency Communication

Commercial Office Building

More STI Products

Frequently Asked Questions About STI

Do STI Stopper covers prevent legitimate emergency use?

Will Stopper III's tamper horn go off every time someone lifts it?

Are STI covers ADA compliant for emergency communication?

Can I install STI covers over any brand of fire pull station?

Do STI weatherproof cabinets need additional weatherproofing?

What's the difference between Stopper II and Stopper III?

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