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CCH · SRB-2A1B
Safety Relay Module for Machine Safety Control
A compact dual-channel safety relay module for monitoring compatible safety-device signals and providing relay interfaces for downstream machine safety control, with selectable NPN / PNP input modes, manual or automatic reset and dedicated muting / shielding inputs.
Typical Integration
ENT Safety Light Curtains
Dual-channel protective-device monitoring
SH Safety Laser Scanners
Compatible safety-signal monitoring where the electrical and safety architecture is appropriate
Machine Safety Control
Relay interface to downstream safety-related circuits
Muting / Shielding Applications
Dedicated MUT_H / MUT_L control inputs within the complete safeguarding architecture
Dual NPN / PNP
Selectable safety input mode
2 NO + 1 NC
Passive relay contacts
<10 ms
Response time
24 VDC ±10%
Operating supply
Safety-performance note:
Cat. 4, PL e and SIL 3 are presented as ratings specified in CCH
SRB-2A1B product documentation. The achieved safety performance of the
complete machine depends on the full input, logic, output, architecture
and validation process.
02 · Core Safety Functions
Core Functions of the SRB-2A1B Safety Relay Module
SRB-2A1B provides safety-device signal monitoring, reset control, diagnostics and relay interfaces for integration into downstream machine safety circuits.
The module should be understood as part of the safety-related control chain. It receives compatible safety-device signals, monitors the configured input condition and provides relay contacts for downstream control.
ENT safety light curtains are a primary integration case. Compatible safety signals from other protective devices, including SH safety laser scanners where the electrical and safety architecture is appropriate, can also form part of an SRB-based control architecture.
01
Dual-Channel Safety-Device Monitoring
SRB-2A1B monitors compatible dual-channel safety-device signals as part of the machine safety-control architecture.
CCH product documentation also describes fault handling when the monitored channels become inconsistent rather than treating an abnormal channel state as a normal synchronized input.
02
Selectable NPN / PNP Input Modes
The module supports selectable dual NPN or dual PNP safety input modes.
The selected input mode should match the actual output architecture of the connected compatible safety device.
03
Manual or Automatic Reset
SRB-2A1B supports configurable manual or automatic reset behavior for different machine safety architectures.
Reset configuration should be selected from the machine risk assessment and should not be confused with permission for hazardous machine motion to restart.
04
2 NO + 1 NC Relay Contacts
SRB-2A1B provides two normally open and one normally closed passive relay contacts for downstream control integration.
Final contact use depends on the actual machine circuit and required safety function.
05
Dedicated Muting / Shielding Inputs
Dedicated MUT_H / MUT_L inputs allow the SRB-2A1B to support the documented muting / shielding control function.
These inputs form part of the complete safeguarding architecture; muting is not a built-in function of the connected ENT safety light curtain.
06
Channel Monitoring and Status Indication
CCH product documentation describes internal monitoring of the input channels together with front-panel status indication for commissioning and maintenance.
CH1, CH2, ERROR and POWER indicators provide visual information about relay-channel, fault and power status.
07
Reverse-Polarity Protection
The documented DC power-input design includes reverse-polarity protection to reduce the risk of module damage from incorrect supply polarity during installation.
Correct supply voltage, polarity and wiring should still be verified before power-up.
08
Fast Safety-Control Response
Current CCH product documentation specifies an SRB-2A1B response time of <10 ms.
This is only one part of total safety-function response time. Protective-device response, downstream control delay and actual machine stopping time must also be considered.
Functional Summary
SRB-2A1B at a Glance
The relay module combines safety-device monitoring, configurable input and reset modes, relay outputs and diagnostic functions. Complete machine safety performance still depends on the surrounding architecture and validation.
| Function | SRB-2A1B Capability | Engineering Consideration |
|---|---|---|
| Safety Input | Compatible dual-channel safety-device signals | Verify the electrical interface of the connected device. |
| Input Mode | Dual NPN / Dual PNP | Match the SRB input mode to the actual protective-device output configuration. |
| Reset | Manual / automatic | Relay reset does not automatically authorize hazardous machine restart. |
| Relay Output | 2 NO + 1 NC passive contacts | Integrate according to the downstream machine safety circuit. |
| Muting / Shielding | Dedicated MUT_H / MUT_L inputs | Use within the complete application-specific muting architecture. |
| Diagnostics | Channel monitoring + CH1 / CH2 / ERROR / POWER indication | Use indicators for commissioning and status diagnosis; final fault handling remains part of the complete control design. |
| Power Protection | Reverse-polarity protection | Does not replace correct wiring and pre-power checks. |
| Response Time | <10 ms | Include SRB response in the complete stopping-time and safety distance evaluation. |
Safety-Control Chain
The Relay Sits Between Detection and Machine Response
A safety relay does not create the protective field and does not stop hazardous motion by itself. It provides the monitoring, logic and relay-interface stage between the safety device and the downstream machine safety control.
Input
Safety Device
ENT, SH or another electrically compatible protective device provides the safety-related input signals.
Monitoring / Interface
SRB-2A1B
Monitors the configured signals, reset condition and applicable control state and provides relay outputs.
Output
Machine Safety Control
Downstream control elements execute the required machine stop, inhibit or other validated safe response.
Selection Principle
Select and configure the SRB around the actual protective device and machine safety architecture. Input type, reset behavior, relay contacts, muting requirements, diagnostics and required safety performance should all be reviewed as part of the complete safety function.
03 · Safety Device Integration
Integrating ENT Safety Light Curtains and SH Safety Laser Scanners
SRB-2A1B can be used as part of the safety-control architecture for compatible dual-channel safety devices. ENT safety light curtains are a primary integration case, while SH safety laser scanner safety signals can also be monitored where the electrical and safety architecture is appropriate.
The key selection question is not simply whether the connected device is a light curtain or a laser scanner. The important issue is whether the safety-related output signals, input mode, electrical interface and complete safety architecture are compatible with the SRB-2A1B.
For this reason, ENT and SH should be treated as two different integration cases rather than assuming one universal wiring diagram applies to every safety device.
Safety Light Curtain Integration
ENT Safety Light Curtains
ENT safety light curtains provide dual OSSD safety outputs for integration into the safety-related control system.
SRB-2A1B can monitor the compatible ENT safety signals and provide relay contacts for downstream machine safety control.
Protective Device
ENT14 · ENT25 · ENT45
Safety Output
Dual OSSD
Input Mode
Match SRB NPN / PNP configuration to the selected ENT output mode
Typical Use
Machine openings · presses · packaging · transfer access
Safety Laser Scanner Integration
SH Safety Laser Scanners
SH safety laser scanners provide safety-related protective signals for area and mobile-machine safeguarding.
Where the electrical interface and safety architecture are appropriate, SRB-2A1B can monitor compatible SH safety signals and provide relay interfaces for downstream machine safety control.
Protective Device
SH Safety Laser Scanner
Safety Function
Protective area / mobile safeguarding
Integration
Verify the actual SH safety output and SRB input compatibility
before final wiring
Typical Use
Robot cells · AGV / AMR · machine-area protection
Integration Principle
Compatible Safety Signal → SRB Monitoring → Machine Safety Control
The same overall control principle applies whether the protective device is a safety light curtain or a safety laser scanner, but the electrical details should be verified for the actual device.
Step 01
Protective Device
ENT or SH detects the safety-relevant condition and provides its defined safety output signals.
Step 02
SRB-2A1B
Monitors the compatible dual-channel safety-device signals according to the selected input configuration.
Step 03
Downstream Safety Circuit
The relay outputs interface with the machine safety-control circuit responsible for the required stop or inhibit response.
Integration Comparison
ENT and SH Use the Same Safety-Control Principle but Different Protective Functions
The SRB role remains the safety-monitoring and relay-interface stage, while the connected protective device determines what kind of hazard access or area is being detected.
| Topic | ENT Safety Light Curtain | SH Safety Laser Scanner |
|---|---|---|
| Protective Geometry | Defined protective line / machine opening | Two-dimensional protective area |
| Typical Application | Machine openings, presses, packaging, transfer points | Robot cells, mobile equipment, machine-area protection |
| SRB Function | Monitor compatible dual-channel safety outputs and provide relay interfaces | Monitor compatible safety signals and provide relay interfaces where the architecture is appropriate |
| Electrical Selection | Match ENT output configuration with the SRB input mode | Verify the specific SH safety-output interface before final wiring |
| Safety Performance | Determined by the complete safety function | Determined by the complete safety function |
Important Integration Boundaries
Do Not Assume Every Safety Device Uses the Same Wiring
Do Not Copy ENT Terminal Assignments to SH
ENT and SH are different protective-device platforms. A terminal assignment or wiring example confirmed for ENT should not automatically be represented as the SH wiring method.
Verify the Actual Safety Output Type
Confirm the connected device’s safety output architecture and electrical characteristics before selecting the SRB input mode and final wiring.
Device Rating Is Not Machine Rating
Connecting a safety device to SRB-2A1B does not automatically make the complete machine Cat. 4, PL e or SIL 3. The complete safety function must be designed and validated accordingly.
Safety Relay Selection Follows the Application
Protective-device type, output signals, reset logic, required safety performance and downstream control circuit should all be reviewed before the final SRB integration is defined.
Documentation Note
Specific SH terminal assignments and wiring diagrams are not shown here unless they are confirmed by the applicable product documentation. Final installation should follow the current device manual and the electrical / safety architecture of the actual machine.
04 · Reset & Restart Logic
Manual Reset, Automatic Reset and Machine Restart Are Different Functions
SRB-2A1B supports manual or automatic reset configuration, but the reset state of the relay should not be confused with permission for hazardous machine movement to restart.
Reset logic defines how the safety relay returns to its ready state after the required input conditions are restored.
Machine restart is a broader control decision. Whether hazardous motion may resume depends on the complete machine safety architecture, the application and the required restart prevention measures.
Reset Mode
Manual Reset
In a manual-reset configuration, the safety relay requires the defined reset action after the protective-device condition has been restored.
This can be appropriate where the machine safeguarding concept requires a deliberate reset action before the safety-related control chain is returned to its ready state.
The final reset arrangement should consider whether the operator can verify that the hazardous area is clear before reset is permitted.
Reset Mode
Automatic Reset
In an automatic-reset configuration, the relay can return to its ready condition when the required safety-device input state is restored.
This does not automatically mean the machine should restart hazardous movement. The downstream machine control still determines whether motion may resume.
Automatic reset should only be used where it is appropriate for the complete safeguarding and machine-control design.
Critical Distinction
Resetting the Safety Relay Is Not the Same as Restarting the Machine
This distinction is important whenever a safety light curtain, safety laser scanner or other protective device is used to stop or inhibit hazardous machine movement.
| Function | What It Means | What It Does Not Automatically Mean |
|---|---|---|
| Protective Field Clear | The connected protective device has returned to its defined clear / safe input condition. | The machine is automatically permitted to restart. |
| Safety Relay Reset | The SRB returns to the appropriate ready state according to the selected reset configuration. | Hazardous movement must immediately resume. |
| Restart Command | The machine control receives the required command or condition to resume operation. | The safeguarded area is necessarily clear unless the complete design ensures this. |
| Hazardous Motion | The machine’s final control system permits or initiates the actual movement. | A function controlled by the SRB reset mode alone. |
Typical Safety Sequence
Think of Reset and Restart as Separate Steps in the Control Chain
The exact machine sequence is application-specific, but the conceptual separation below helps avoid unsafe or misleading assumptions.
01
Protective Device Is Interrupted
ENT, SH or another compatible protective device changes its
safety-related output state in response to the detected condition.
02
SRB Safety Outputs Respond
The safety relay responds according to the monitored input state and
the downstream safety circuit acts to stop or inhibit the hazardous
machine function.
03
Protective Condition Is Restored
The protective device returns to its defined normal condition after
the interruption or access event has ended.
04
Reset Condition Is Satisfied
The SRB returns to its ready state according to the selected manual
or automatic reset configuration.
05
Machine Restart Is Controlled Separately
Any restart of hazardous motion must follow the machine’s validated
restart logic and the applicable safeguarding design.
Reset Mode Selection
Choose Reset Behavior From the Application — Not Convenience Alone
Can a Person Remain in the Hazardous Area?
If someone could pass through the protective device and remain inside the safeguarded area, restart prevention and reset location become especially important parts of the machine safety design.
Can the Operator See the Hazard Area?
Manual reset arrangements should consider whether the person performing the reset has appropriate visibility of the safeguarded area and can verify the required condition before reset.
Is the Protective Device Used for Access or Process Detection?
The role of the connected ENT, SH or other device affects how reset and restart logic should be designed in the complete machine control system.
What Does the Downstream Control Do After Reset?
The system designer should verify whether relay recovery only enables the control circuit or whether another deliberate machine start command is required before hazardous motion can resume.
Safety Principle
“Protective Field Clear” Should Never Be Treated as a Universal Restart Command
A clear light curtain or scanner field means the protective device has returned to its defined normal condition. It does not by itself confirm that every hazard is clear or that hazardous movement may safely restart.
Reset behavior and restart behavior should therefore be defined separately within the complete machine safety architecture.
Engineering Note
SRB-2A1B provides manual / automatic reset configuration; it does not determine the complete restart strategy of the machine. Final reset, restart and restart-prevention logic should be established from the machine risk assessment and validated safety-control design.
05 · Muting / Shielding Control
How SRB-2A1B Supports Safety Light Curtain Muting and Shielding Logic
SRB-2A1B includes dedicated MUT_H and MUT_L control inputs for muting / shielding applications, allowing the safety relay to form part of a complete material-transfer safeguarding architecture.
Muting should not be understood as a feature built into the ENT safety light curtain. ENT continues to monitor the protective field, while external sensing and the SRB safety-control architecture provide the additional logic required for the documented material-transfer function.
The MUT_H / MUT_L inputs belong to the SRB control stage. They should therefore be considered together with the external sensing, relay interfaces and actual machine operating sequence.
Dedicated Control Inputs
MUT_H and MUT_L Are Part of the SRB Muting / Shielding Function
These inputs provide the control interface for the documented muting / shielding mode. They do not independently determine whether an entering object is a person or permitted production material.
SRB Control Input
MUT_H
MUT_H is one of the dedicated muting / shielding control inputs on the SRB-2A1B.
Its use should follow the applicable SRB product documentation and the defined application wiring rather than being treated as a standalone material-detection input.
SRB Control Input
MUT_L
MUT_L forms the corresponding part of the documented SRB muting / shielding control interface.
The final state of MUT_H and MUT_L should be derived from the confirmed external sensing and relay architecture for the actual machine.
Documented CCH Architecture
SRB-2A1B Is One Part of the Complete Muting System
In the documented CCH application, four functional elements work together rather than assigning the whole muting function to one device.
Protective Detection
ENT Safety Light Curtain
Detects interruption of the protected opening and provides the safety-related protective-device signals.
External Recognition
2 Photoelectric Sensors
Provide the additional signals used in the documented person-versus-material recognition logic.
Signal Interface
2 Ordinary Relays
Collect and convert the external recognition signals in the documented arrangement.
Safety Control
SRB-2A1B
Uses the compatible protective-device and muting / shielding control signals as part of the complete safety architecture.
Documented Configuration
ENT Safety Light Curtain
+ 2 External Photoelectric Sensors
+ 2 Ordinary Relays
+ SRB-2A1B
Final sensor positioning, wiring and downstream machine response
remain application-specific.
Functional Responsibilities
Keep Protective Detection, Recognition and Muting Logic Separate
Clear separation between these functions prevents the common mistake of describing the light curtain, external sensors or safety relay as independently providing the whole muting function.
| Component | Primary Role | Do Not Describe It As |
|---|---|---|
| ENT Safety Light Curtain | Protective-field detection and safety-related output signals. | A device with built-in person / material recognition or built-in muting. |
| External Photoelectric Sensors | Additional sensing signals for the documented recognition logic. | Complete muting devices by themselves. |
| Ordinary Relays | Signal collection and conversion within the documented external sensing path. | The safety relay module itself. |
| MUT_H / MUT_L | SRB control inputs used within the documented muting / shielding function. | Independent sensors that detect a pallet or person. |
| SRB-2A1B | Safety-device monitoring, relay interface and muting / shielding control within the appropriate architecture. | A complete standalone muting solution without external sensing and machine integration. |
Documented Recognition Logic
External Sensors Provide the Person-versus-Material Information
In the documented CCH scheme, the two external photoelectric sensors provide the recognition condition used around the SRB muting / shielding architecture.
Only One External Sensor Blocked
The documented logic treats this condition as personnel entering the protected area.
Both External Sensors Blocked Simultaneously
The documented logic treats this condition as material entering the protected area.
Application Boundaries
Do Not Turn the Documented Architecture Into a Universal Template
No Universal Sensor Placement
External sensor positions should be selected from the actual load dimensions, machine opening, travel direction and personnel access conditions.
No Universal Time Window
This page does not define one fixed muting duration or timing rule for every conveyor, palletizer or packaging machine.
No Universal T / L / Four-Sensor Layout
The documented CCH architecture uses two external photoelectric sensors and should not be rewritten as a generic T-, L- or four-sensor configuration.
No Universal ENT Model
The exact safety light curtain should be selected according to resolution, protection height, sensing distance, response time, mounting and the actual application.
Engineering Note
MUT_H and MUT_L should be treated as SRB control inputs within a complete muting / shielding architecture. They do not eliminate the need to define the external sensing, personnel-access condition, material-transfer logic and downstream machine safety response for the actual application.
06 · Wiring & Terminal Reference
SRB-2A1B Wiring and Terminal Reference
The SRB-2A1B documentation defines separate terminals for safety-device monitoring, reset control, muting / shielding control and relay outputs. These references are useful for selection and project discussion, but they should not be treated as a complete machine wiring drawing.
For the documented ENT integration, the safety light curtain’s OSSD1 and OSSD2 outputs are connected to S12 and S22, and the SRB input mode is selected to match the connected ENT NPN / PNP output configuration.
Reset and muting use separate control terminals. This separation is important because safety-device monitoring, relay reset and muting are different functions within the control architecture.
Documented Integration Modes
Three SRB-2A1B Control Arrangements
The current CCH documentation shows manual reset, automatic reset and an SRB muting state as separate control configurations.
Mode 01
ENT + Manual Reset
The ENT dual safety outputs are monitored by S12 and S22, while an external reset switch is connected in the SR / SRC reset path.
OSSD1 → S12
OSSD2 → S22
SRC → External Reset Switch → SR
OSSD2 → S22
SRC → External Reset Switch → SR
Mode 02
ENT + Automatic Reset
In the documented SRB muting state, the connected safety light curtain signal does not affect the relay module.
The same documented dual-channel ENT monitoring is used, while SR and SRC are directly connected for the SRB automatic-reset configuration.
OSSD1 → S12
OSSD2 → S22
SRC ↔ SR
OSSD2 → S22
SRC ↔ SR
Mode 03
Documented SRB Muting State
CCH documentation identifies the SRB muting state using the dedicated MUT_H and MUT_L terminals.
MUT_H → 24 V
MUT_L → 0 V
MUT_L → 0 V
This documented relay state is not by itself a complete machine-level muting design.
ENT Safety Light Curtain Input
Documented Dual-Channel ENT Connection
The following input assignments are specifically documented for the safety light curtain integration case.
ENT OSSD1
→
SRB S12
First monitored safety-light-curtain output channel.
ENT OSSD2
→
SRB S22
Second monitored safety-light-curtain output channel.
ENT Output Mode
→
SRB NPN / PNP Selector
Match the relay input mode to the actual ENT output configuration.
Quick Terminal Reference
Principal SRB-2A1B Control and Relay Terminals
These are the principal connections used in the documented CCH examples. Always verify the current product instructions before final wiring.
| Terminal | Documented Function | Important Boundary |
|---|---|---|
| S12 | Safety light curtain OSSD1 monitoring input. | Documented here for ENT light-curtain integration; do not automatically copy this assignment to every safety device. |
| S22 | Safety light curtain OSSD2 monitoring input. | Use together with the correct NPN / PNP input configuration. |
| SR / SRC | Reset-control connection for manual or automatic reset configuration. | Reset configuration does not itself define machine restart permission. |
| MUT_H / MUT_L | Dedicated SRB muting / shielding control terminals. | These are control inputs, not external person / material sensors. |
| 13–14 | Normally open relay contact pair 1. | Final circuit use depends on the downstream machine safety architecture. |
| 23–24 | Normally open relay contact pair 2. | Final circuit use depends on the downstream machine safety architecture. |
| 41–42 | Normally closed auxiliary relay contact pair. | Do not describe the auxiliary contact as a substitute for the required safety-output architecture. |
2A1B Relay Output
Two Normally Open Contacts + One Normally Closed Auxiliary Contact
NO Contact 01
13–14
First normally open passive relay contact pair for downstream control integration.
NO Contact 02
23–24
Second normally open passive relay contact pair for downstream control integration.
NC Auxiliary
41–42
Normally closed auxiliary relay contact pair for the appropriate control / status function defined by the machine design.
SH Safety Laser Scanner Integration
Do Not Reuse the ENT Terminal Example as an Unverified SH Wiring Diagram
SRB-2A1B can monitor compatible SH safety signals where the electrical and safety architecture is appropriate, but the OSSD1 → S12 / OSSD2 → S22 example shown above is documented here specifically for the safety light curtain integration case.
The actual SH safety-output interface should be confirmed from the applicable scanner documentation before terminal assignments are published or used for installation.
Before Power-Up
Verify the Complete Wiring Before Commissioning
Remove Power Before Wiring
Wiring, terminal changes and relay installation should be completed with the relevant electrical power removed.
Verify Terminal Identification
Confirm the current SRB documentation, connected safety-device outputs and terminal assignments before energizing the circuit.
Match the NPN / PNP Mode
The relay input selector must correspond to the actual output mode of the connected compatible safety device.
Validate the Complete Safety Function
Test protective-device response, reset behavior, relay outputs, downstream machine response and any muting function before the machine is returned to service.
Wiring Scope
These wiring references are selection and integration aids, not complete machine electrical drawings. Final installation must follow the current SRB-2A1B instructions, the connected safety-device documentation, the machine electrical design and the validated safety architecture.
07 · Safety Performance & Technical Specifications
SRB-2A1B Safety Performance and Technical Specifications
CCH product documentation specifies the SRB-2A1B with Cat. 4, PL e and SIL 3 safety ratings together with electrical, timing, environmental and mechanical data for safety-control integration.
These ratings describe the SRB-2A1B component as stated in CCH product documentation. They should not be interpreted as an automatic rating for the complete machine.
The achieved safety performance of the complete safety function also depends on the connected protective device, input architecture, diagnostics, downstream final control elements, reset logic, wiring and validation.
Important Distinction
Component Rating Does Not Automatically Become the Machine Rating
Installing an SRB-2A1B together with a Type 4 safety light curtain or another safety-rated protective device does not automatically prove that the complete machine safety function achieves Cat. 4, PL e or SIL 3.
The complete safety-related control system must be designed, calculated and validated according to the required machine safety performance.
Technical Data
SRB-2A1B Electrical, Environmental and Mechanical Specifications
The following values summarize the principal specifications currently stated in CCH SRB-2A1B product documentation.
| Parameter | SRB-2A1B | Engineering Note |
|---|---|---|
| Operating Voltage | 24 VDC ±10% | Confirm supply voltage and polarity before energizing the module. |
| Rated Power | <3 W | Include the module in the control-cabinet power budget. |
| Safety Input | Dual NPN or Dual PNP | Select the input mode to match the connected compatible safety device. |
| Relay Output | 2 NO + 1 NC passive contacts | 13–14 and 23–24 are normally open; 41–42 is the normally closed auxiliary contact. |
| Contact Capacity |
AC15: 5 A / 250 V DC13: 6 A / 24 V |
Confirm the actual downstream load and switching requirement before final circuit design. |
| Electrical Life | ≥1,000,000 operations | Actual service life depends on switching conditions and applied load. |
| Response Time | <10 ms | Include this time in the complete protective-device and machine stopping calculation. |
| Pull-In Delay | <50 ms | Relay timing should be considered together with the complete control sequence. |
| Power-On Startup | <1 s | Represents the documented module startup characteristic. |
| Operating Temperature | −30 to +50°C | No frost or condensation. |
| Storage Temperature | −40 to +70°C | Store within the documented environmental limits. |
| Operating Humidity | 35–85% RH | Avoid condensation. |
| Storage Humidity | 35–95% RH | Follow the documented storage conditions. |
| Protection Rating | IP20 | Installation environment and enclosure protection should be selected for the actual control cabinet and machine. |
| Dimensions | 114.5 × 99.5 × 22.5 mm | Compact DIN-rail control-cabinet format. |
| Mounting | 35 mm DIN rail | |
| Terminal Design | Detachable terminals | Supports control-cabinet installation and wiring maintenance; final connections should follow the current SRB-2A1B documentation. | Secure the module mechanically before final wiring and commissioning. |
Timing Characteristics
Relay Timing Is Only One Part of the Total Safety Response
When the SRB is used with an ENT safety light curtain, SH safety laser scanner or another compatible protective device, the total system response includes more than the relay response time alone.
SRB Response
<10 ms
Documented response time of the SRB-2A1B module.
Pull-In Delay
<50 ms
Documented pull-in timing characteristic for the relay module.
Startup
<1 s
Documented power-on startup time.
Standards Referenced in Product Documentation
Functional Safety and EMC Framework
CCH SRB product documentation references functional-safety and EMC standards associated with the relay module. The presence of a standard reference should not be interpreted as a substitute for the complete machine risk assessment or system validation.
EN ISO 13849
Referenced in the SRB documentation in association with the stated
Category 4 and PL e performance.
IEC 61508
Referenced in the product documentation together with the stated
SIL 3 safety-integrity rating.
IEC 62061
Listed in the SRB documentation as part of the machinery
functional-safety framework.
EN 61000-4 Series
EMC immunity standards referenced in the current SRB product
documentation, including electrostatic discharge, radiated RF,
EFT, conducted RF and power-frequency magnetic-field testing.
Installation Environment
Design the Control Cabinet Around the Relay’s Actual Limits
IP20 Is Not a Field-Sensor Enclosure Rating
SRB-2A1B is a DIN-rail safety-control module. The final cabinet or enclosure should provide the environmental protection required by the machine installation.
Avoid Frost and Condensation
The documented operating-temperature range is −30 to +50°C with no frost or condensation. Cabinet thermal and humidity conditions should remain within the product limits.
Verify the Contact Load
Relay-contact capacity should be checked against the actual downstream voltage, current and load category rather than selected from contact count alone.
Validate After Installation
Safety-device response, reset logic, muting logic where used, relay outputs and downstream machine response should be checked before the machine is returned to service.
Certification & Documentation Boundary
Do Not Turn a Product Rating Into an Unsupported Certification Claim
Cat. 4, PL e and SIL 3 are presented on this page as ratings stated in current CCH SRB-2A1B product documentation.
This page does not currently claim an independent third-party TÜV functional-safety certificate for the SRB-2A1B unless a corresponding certificate, certificate number and product scope are separately available and verified.
Likewise, the standards referenced in the product documentation should not be presented as proof that every machine using the SRB automatically achieves the same Category, Performance Level or SIL.
Engineering Note
Use the exact selected safety device, SRB configuration, downstream control circuit and measured machine stopping performance when validating the complete safety function. Component specifications are engineering inputs; they are not a substitute for machine-level safety design and validation.
08 · FAQ, Resources & Project Support
Safety Relay Module FAQ
Common questions about SRB-2A1B safety-device monitoring, NPN / PNP inputs, reset logic, muting control, relay outputs and machine safety integration.
1. What does a safety relay module do?
A safety relay module monitors compatible safety-device signals and provides relay interfaces for downstream machine safety control. SRB-2A1B forms the logic and relay-interface stage between the protective device and the machine control circuit.
2. Can SRB-2A1B work with ENT safety light curtains?
Yes. ENT safety light curtains are a primary integration case. Their dual OSSD safety outputs can be monitored by the SRB-2A1B using the documented dual-channel input arrangement and the appropriate NPN / PNP configuration.
3. Can SRB-2A1B monitor SH safety laser scanner signals?
Yes, where the electrical interface and safety architecture are appropriate. The actual SH safety output and SRB input compatibility should be verified before final wiring. ENT terminal examples should not automatically be copied to SH.
4. Does SRB-2A1B support NPN and PNP safety inputs?
Yes. SRB-2A1B supports selectable dual NPN or dual PNP input modes. The selected mode should match the actual safety-device output configuration.
5. What is the difference between manual and automatic reset?
Manual reset requires the defined reset action before the relay returns to its ready state. Automatic reset allows the relay to recover when the required input condition is restored. Automatic reset does not automatically mean hazardous machine motion should restart.
6. Can the machine automatically restart when the safety device becomes clear?
A clear safety light curtain or scanner field should not by itself be interpreted as permission for hazardous motion to restart. Reset and machine restart should be handled as separate functions within the validated safety-control architecture.
7. Does SRB-2A1B support safety light curtain muting?
SRB-2A1B includes dedicated MUT_H / MUT_L control inputs used within the documented CCH muting / shielding architecture. Muting is not a built-in function of the ENT safety light curtain and should be treated as a complete system function. See the Safety Light Curtain Muting Guide .
8. What relay outputs does SRB-2A1B provide?
SRB-2A1B provides 2 normally open + 1 normally closed passive relay contacts. The documented contact pairs are 13–14, 23–24 and 41–42.
9. What is the response time of SRB-2A1B?
Current CCH product documentation specifies a response time of <10 ms. This is only one part of the total safety response; the protective-device response, downstream control delay and actual machine stopping time must also be considered.
10. Does SRB-2A1B automatically make the complete machine Cat. 4, PL e or SIL 3?
No. Cat. 4, PL e and SIL 3 are ratings stated in current CCH SRB-2A1B product documentation. The achieved safety performance of the complete machine depends on the full input, logic, output, architecture and validation process.
11. Is SRB-2A1B only used with safety light curtains?
No. It should be considered a safety-control component for compatible safety-device signals. ENT safety light curtains are one important application, and compatible SH safety laser scanner safety signals can also be monitored where the electrical and safety architecture is suitable.
12. Can I use the wiring example on this page for every safety device?
No. The documented OSSD1 → S12 and OSSD2 → S22 example is presented for the ENT safety light curtain integration case. Other protective devices should be wired according to their applicable product documentation and verified electrical compatibility.
13. What information should I provide for SRB-2A1B selection or integration?
Useful information includes the connected safety device and exact model, output signal type, NPN / PNP requirement, reset strategy, downstream control circuit, muting requirement if applicable, machine supply voltage and the required machine safety performance.
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Muting Guide
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Application Engineering
Need Help Integrating SRB-2A1B Into a Machine Safety Circuit?
Send us the protective-device model, safety output information and machine-control requirements. We can help review the appropriate SRB input mode, reset strategy, relay interface and muting requirements for the application.
Safety Device
ENT · SH · output signal type
Control Logic
Reset mode · muting requirement · safety function
Machine Interface
Supply · downstream circuit · required safe response
Engineering scope: this page provides product-level selection and integration information for the SRB-2A1B. Final device compatibility, wiring, reset strategy, muting logic, safety performance and machine validation must be determined for the actual safety function and installation.