Emergency Stop Push Buttons (KOB Series)
Industrial Emergency Knock-Off Palm Switches | IP65 | Twist + Pull to Release
Reliable Safety Control for Industrial & Pneumatic Systems
The KOB Series Emergency Stop Push Buttons provide fast, unmistakable shut-down for machinery, pneumatic systems, and process-control panels.
Each unit features a durable thermoplastic enclosure, bright red mushroom head, and a twist + pull release mechanism to prevent accidental reset.
Engineered for harsh industrial environments, the KOB range offers IP65 protection, Class II double insulation, and compliance with IEC 60947-5-1 and UL 508 standards.
KOB Range Overview
Choose from three variants to suit your control-station layout and safety requirements:
KOB-1 – Standard Emergency Stop Button
Ø 40 mm red mushroom head
1 NC + 1 NO snap-action contact block
Twist + Pull release for deliberate reset
Compact 68 × 68 × 50 mm enclosure
Suitable for panel or wall mounting
KOB-S1 – Emergency Stop with Protective Shroud
Raised yellow guard ring prevents accidental activation
Ideal for busy workstations or mobile machinery
Same 1 NC + 1 NO contact configuration
Maintains IP65 protection and full electrical ratings
KR-KOB-1 – Key-Release Emergency Stop
Twist + Key release mechanism for controlled reset
Used where supervisor or authorised reset is required
Includes removable key with locking function
Meets safety standards for guarded or locked restart
Key Technical Features
Electrical Specifications
| Parameter | Value |
|---|---|
| Rated Insulating Voltage (Ui) | 690 V AC |
| Rated Impulse Voltage (Uimp) | 8 kV |
| Thermal Current (Ith) | 10 A @ 40 °C in free air |
| Contact Rating (UL 508) | A600 (120–600 V AC > 10 A), Q300 (125–300 V DC > 1 A) |
| Rated Operational Current – AC-15 (50–60 Hz) | 24 V AC 10 A / 240 V AC 6 A / 400 V AC 4 A |
| Rated Operational Current – DC-13 | 24 V DC 2.8 A / 125 V DC 0.55 A / 250 V DC 0.27 A |
| Contact Resistance | ≤ 25 mΩ |
| Short-Circuit Protection | 10 A gG fuse (500 V AC min) |
Mechanical & Environmental
| Parameter | Value |
|---|---|
| Operating Temperature | −40 °C to +70 °C |
| Mechanical Durability | 300 000 operations |
| B10d Reliability Metric | 600 000 operations |
| Max Switching Frequency | 3 600 cycles/hour |
| Ingress Protection | IP65 – dust-tight and water-resistant |
| Pollution Degree | 3 – industrial environment |
| Insulation Class | Class II (double insulated) |
| Cable Capacity | 0.5 – 2.5 mm² (1 or 2 conductors) |
Compliance & Standards
Safety and Certification
CE & UKCA Marked for European and UK use
IEC 60947-5-1 / EN 60947-5-1 compliant
UL 508 A600 / Q300 listed for industrial control equipment
Pollution Degree 3 for factory and process environments
Class II construction – no protective earth required
Typical Applications
Pneumatic control panels and air-distribution systems
Machine tools and automated assembly lines
Process-valve stations and test rigs
Packaging, bottling, and conveyor machinery
Safety interlock and operator control boxes
Product Highlights
Why Choose the KOB Series?
Compact design with professional appearance
Snap-action, silver-plated contacts ensure long life and low resistance
Easy field wiring through dual M20 knockouts
40 mm mushroom for fast access – clear operator feedback
Optional S1 guarded or KR key-release versions for enhanced safety control
Technical Resources
Downloads
KOB Palm Switch with Emergency Ø 40 mm Mushroom – PDF Datasheet
Declaration of Conformity (CE / UKCA)
Order Information
Model: KOB-1 / KOB-S1 / KR-KOB-1
Description: Emergency Knock-Off Palm Switch with Ø 40 mm Mushroom Head, IP65, 1 NC + 1 NO
Tariff Code: 85371098
Brand: Connexion Developments Ltd
Related Products
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Push-in pneumatic fittings and tubing – complete control-panel solutions
See More Emergency Stop Devices.
Frequently Asked Questions – Emergency Stop Push Buttons
What does A600 / Q300 mean?
These are UL 508 contact ratings defining how much current the switch can safely handle.
A600 applies to AC control circuits (up to 600 V AC, 10 A).
Q300 applies to DC circuits (up to 300 V DC, 1 A).
Both confirm the KOB series is built for industrial control duty.
What is the difference between AC-15 and DC-13?
These are IEC utilisation categories describing the type of load being switched:
AC-15 → control of electromagnetic loads (contactors, solenoids) on AC circuits.
DC-13 → the same, but for DC circuits.
The KOB contacts are rated up to 400 V AC (4 A) and 250 V DC (0.27 A) respectively.
What does B10d mean?
B10d is a reliability figure: it’s the number of operations after which 10 % of devices are expected to have dangerous failures.
For the KOB, B10d = 600 000 cycles, meaning an exceptionally long safety life for an emergency-stop device.
What does “Conventional thermal current Ith = 10 A” mean?
It’s the maximum continuous current the contacts can carry without overheating in 40 °C ambient air.
It confirms the KOB can handle up to 10 A continuous load safely.
What is the rated impulse voltage 8 kV?
It’s the voltage surge the insulation can withstand — short transients such as lightning or switching spikes.
An 8 kV rating indicates excellent insulation strength for industrial environments.
What does Pollution Degree 3 mean?
Pollution Degree 3 refers to industrial environments where conductive dust or moisture may be present.
It ensures the switch spacing and insulation are designed to cope with these harsher conditions.
How does the twist + pull release work?
After activation, the mushroom head locks in place.
To reset, the operator must twist the head to release the latch, then pull it outward.
This two-step action prevents accidental reset and complies with EN 60947-5-1 safety design.
What does IP65 mean?
IP65 = completely dust-tight and resistant to water jets.
Your KOB switch can be used indoors or outdoors in typical industrial settings without additional sealing.
What is the contact resistance of 25 mΩ?
It’s the electrical resistance through the closed contacts — very low to ensure minimal voltage drop and heat rise.
The lower the milliohm value, the better the conductivity and switch longevity.
Can the KOB series be used in 24 V DC control panels?
Yes. The KOB is fully rated for 24 V DC at 2.8 A (DC-13), making it ideal for PLC and pneumatic control circuits.
Is the KOB series CE and UKCA approved?
Yes. Every unit is fully CE / UKCA marked, tested to IEC 60947-5-1 and UL 508, ensuring compliance with European and UK machinery-safety directives.
Installation & Wiring Best Practices
Correct Mounting Orientation
Install the emergency stop switch in a clearly visible and easily accessible position.
The red mushroom actuator must be horizontal and unobstructed, ideally within arm’s reach of the operator’s normal working position.
Avoid placing it where accidental activation could occur — particularly for mobile or vibrating equipment.
Enclosure & Sealing
The KOB series enclosure is IP65 rated, but reliable sealing depends on proper cable entry.
Use M20 cable glands or flexible conduit fittings with compatible gaskets.
Ensure unused knockouts are sealed with IP-rated plugs to maintain ingress protection.
Electrical Connections
Terminate conductors using correctly sized ferrules or crimp lugs (0.5–2.5 mm²).
Tighten the screw terminals securely — loose connections cause heat and voltage drop.
Follow the colour code convention (e.g. brown for L+, blue for L– / neutral, green-yellow for earth if used).
For Class II double-insulated devices, no protective earth is required.
Contact Configuration and Circuit Use
Each KOB unit includes 1 Normally Closed (NC) and 1 Normally Open (NO) contact block:
Use the NC contact to interrupt the control circuit or energise a safety relay when opened.
The NO contact can provide indication (lamp or PLC input) when the button is pressed.
In safety-critical circuits, route the NC contact through a dual-channel safety relay to meet EN ISO 13849-1 requirements.
Testing and Commissioning
After wiring:
- Verify correct operation with the machine power off.
- Press the button to ensure it latches positively.
- Reset by twist + pull (or key release, depending on model).
- Confirm that power is interrupted and restored correctly.
- Record test results in the machine’s safety logbook.
Maintenance & Inspection
Inspect emergency stop devices at least every six months, or per site risk assessment.
Check for:
Damaged actuators or faded colours
Loose cable glands or cracked enclosures
Electrical continuity across contacts
Proper reset function after activation
Replace any unit that shows wear, corrosion, or mechanical damage.
Safety Reminder
Emergency stops are complementary safety measures, not substitutes for functional or interlocked protection systems.
Always integrate them within a certified safety circuit (Category 3 or 4 per EN ISO 13849-1) and ensure operators are trained in their correct use.
Order Online – Fast UK & EU Delivery
The KOB Series Emergency Stop Push Buttons from Connexion Developments Ltd combine reliability, industrial durability, and safety compliance in one compact, professional design.
Every unit is fully tested and CE / UKCA approved, offering dependable protection for control panels, pneumatic systems, and automated machinery.
With three models available — Standard (KOB-1), Shrouded (KOB-S), and Key-Release (KOB-K) — you can select the perfect configuration for your application.
Each unit arrives pre-assembled, ready for wiring, and protected to IP65 for use in demanding environments.
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Product Reviews.
Better than expected, delivery quick too and very well priced. Thanks. If I need more will be back. Dan.
★★★★★
Reviewed on 21/03/2018 by Daniel W
Quick delivery, my engineer is now happy and my MD even more so as these are very well priced.
★★★★★
Reviewed on 01/06/2020 by Zara Martin