STI-6518
ActiveStopper II Push Button Cover with Horn
STI Stopper II — protective polycarbonate cover for push buttons with built-in horn.
Common Applications
The red protective cover over emergency buttons and fire alarm pull stations in every school, hospital, and commercial building. Lift the cover to access the button underneath — the built-in horn sounds when the cover is raised, deterring false alarms. Polycarbonate is virtually unbreakable. The most recognizable safety product in commercial buildings.
Specifications
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Certifications
Third-party safety certifications. UL = required for US NEC installations. CE = EU compliance. CSA = Canadian standards.
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UL, CE, ADA
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Color
Button/actuator color. Green = start/go, Red = stop/emergency, Yellow = caution, Blue = reset (per IEC 60204-1).
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Red
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Material
The bezel/body material. Metal bezels are more durable in harsh environments. Plastic is lighter and cheaper.
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Polycarbonate
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Mounting Type
How the button attaches to the panel. Panel mount is standard — installs through a cutout from the front.
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Surface mount over existing button
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Installation Quick Reference
Panel cutout: 22mm. Insert from the front of the panel, secure with mounting nut from behind (tighten to 2-3 Nm).
Contact block: Snap or screw the contact block onto the rear of the button body. Ensure the contact block orientation matches the wiring diagram — NO terminals are usually marked.
Wiring: Use 0.5-2.5mm² stranded wire with ferrules. Tighten screw terminals to 0.8 Nm. Test the button function before energizing the circuit.
Dimensions
Troubleshooting
Button doesn't respond when pressed
Check the contact block first — it's the most common failure point. Test continuity across the NO or NC terminals with a multimeter. If no click is felt, the return spring in the head may be broken.
Works intermittently
Contact block contacts are pitted or burned. Replace the contact block — don't try to file the contacts. Check if the rated cycle count has been exceeded.
Button feels mushy or doesn't click
The spring return mechanism in the button head is worn. Replace the head. The contact block can usually be reused if it tests OK.
Where to Buy
Price range
$55.28 — $98.38
across 2 distributors
Quick Specs
- Certifications
- UL, CE, ADA
- Color
- Red
- Material
- Polycarbonate
- Mounting Type
- Surface mount over existing button
What People Are Saying
“The red protective cover over emergency buttons and fire alarm pull stations in every school, hospital, and commercial building. Lift the cover to access the button underneath — the built-in horn soun”