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Brand: Allen-Bradley
Allen-Bradley 440R-N23135 MSR127RP Safety Relay 24V AC/DC
Description
A 24V AC/DC MSR127RP safety relay with monitored manual reset
The Allen-Bradley 440R-N23135 is the MSR127RP version of the Minotaur MSR127 monitoring safety relay. It has three N.O. safety outputs and one N.C. auxiliary output, runs on 24V AC/DC, uses a manual monitored reset, and has removable screw terminals. It is only 22.5 mm wide, so a full stop-circuit stage takes very little rail space.
The R in the type name means that the reset button must be pressed and released: the relay will not re-enable on its own when the guard closes. The P means a plug-in terminal block, which lets a technician swap the relay without disturbing the field wiring.
Technical specifications
| Parameter | Specification |
|---|---|
| Catalog number | 440R-N23135 |
| Type | MSR127RP, Guardmaster Minotaur monitoring safety relay |
| Supply voltage | 24V AC/DC (0.85 to 1.1 x rated, 50/60 Hz) |
| Reset | Manual monitored (feedback loop S12-S34) |
| Safety outputs | 3 N.O. |
| Auxiliary output | 1 N.C. (terminals 41-42) monitors the safety output state |
| Terminals | Removable screw terminals |
| Power consumption | 2 W |
| Weight (24V AC/DC) | 210 g |
| Functional safety (ISO 13849-1) | PLe, Category 4; MTTFd 378 years; DC average 99% |
| Functional safety (IEC 62061 / 61508) | SIL CL 3; PFH 1.94E-09 per hour; HFT 1; proof test interval 20 years |
| Safety inputs | 1 N.C., 2 N.C. or 2 PNP light curtain; infinite simultaneity; 110 ohm maximum input resistance |
| Response time / recovery time | 15 ms / 100 ms |
| Power-on delay | 1 s |
| Output rating | UL B300 5 A / 240V AC; AC-15 5 A / 250V AC; DC-13 3 A / 24V DC |
| External output fuse | 6 A slow blow or 10 A quick blow |
| Minimum switched load | 10 mA / 10 V |
| Contact material | AgSnO2 + 0.5 micron Au |
| Electrical life | 100,000 operations at 220V AC / 4 A; 1,000,000 at 30V DC / 2 A |
| Mechanical life | 10,000,000 cycles |
| Operating temperature | -5 to +55 C |
| Enclosure protection | IP40 (NEMA 1); terminals IP20; mount in an enclosure of at least IP54 |
| Conductor size / torque | 0.2 to 2.5 mm2 (24 to 12 AWG); 0.6 to 0.8 N-m |
| Mounting / width | 35 mm DIN rail; 22.5 mm wide |
Wiring and reset behavior
The installation instructions show single-channel N.C. wiring up to PLc, dual-channel three-wire wiring up to PLd, and dual-channel four-wire wiring or a 24V DC signal up to PLe. In the four-wire arrangement cross-loop monitoring is switched on, and a cross fault must be cleared with a fault reset. Single-channel inputs and 24V DC signals have cross-loop monitoring disabled.
In manual monitored mode a positive edge on the reset circuit is needed after the safety inputs have closed. If the reset circuit stays closed while the inputs are open, a reset fault occurs. The feedback contacts of the controlled contactors are placed in series with the reset circuit, so a welded contactor prevents a restart.
Where it is used
Typical duties are a single E-stop or interlocked gate feeding two contactors, as in the example circuit with an 800F emergency stop, an MSR relay and a 100S contactor. The CH1 and CH2 indicators show each output channel, and PWR flashes green when a cross-loop fault is detected.
MSR127 relays are not repairable. If a unit fails, replace it before the machine is allowed to run, and keep a record of the replacement as part of the safety documentation. The product is part of a safety function, so a risk assessment must confirm that the ratings above suit the machine.
Related Allen-Bradley products: Allen-Bradley 440C-CR30-22BBB CR30 Configurable Safety Relay, Allen-Bradley 440R-N23124 MSR127T Safety Relay 230V AC and Allen-Bradley 440R-ENETR GSR EtherNet/IP Interface.
Ordering and documents
Order 440R-N23135 exactly as printed. The hosted document is the MSR127 installation instructions 440R-IN079D, and the photo is the official Rockwell product photograph of this part. Other safety devices are listed in the Safety Switches & Guard Locking category.
Seven Star LLC is an independent supplier in Muscat and quotes on request. Please confirm the catalog number, ratings and the current product status against the latest Rockwell Automation documents before ordering.
Datasheets & Documents
- Installation instructions MSR127 Minotaur Monitoring Safety Relays Installation Instructions (440R-IN079) Download
Reviews (0)
About brand
Allen-Bradley is the brand of Rockwell Automation for industrial control: ControlLogix and CompactLogix controllers, I/O systems, PanelView operator terminals, PowerFlex drives, motor control and industrial network equipment. The company began in Milwaukee in 1903, when Lynde Bradley and Dr. Stanton Allen formed the Compression Rheostat Company to make the motor speed controller Bradley had invented in 1901. It took the name Allen-Bradley in 1909 and was bought by Rockwell International in 1985. Since 2001 its owner has been Rockwell Automation, which is still headquartered in Milwaukee, Wisconsin.
Allen-Bradley company profile
| Founded | 1903, Milwaukee, Wisconsin, USA, as the Compression Rheostat Company |
|---|---|
| Founders | Lynde Bradley (inventor of the compression rheostat, 1901) and Dr. Stanton Allen (investor); Harry Bradley joined in 1904 |
| Name | Allen-Bradley Company from 1909 |
| Ownership | Acquired by Rockwell International in 1985 for about USD 1.65 billion; a brand of Rockwell Automation (NYSE: ROK) since 2001 |
| Headquarters | Milwaukee, Wisconsin, USA |
| Product families | Logix programmable automation controllers (ControlLogix, CompactLogix), legacy SLC 500 and MicroLogix PLCs, Micro800 controllers, POINT, FLEX and Compact I/O, PanelView HMIs, PowerFlex AC drives, contactors, motor starters and soft starters, safety components, Stratix Ethernet switches |
Milestones
- 1901: Lynde Bradley invents the compression rheostat to control the speed of electric motors.
- 1903: The Compression Rheostat Company is formed in Milwaukee with an initial investment of USD 1,000.
- 1904: Harry Bradley joins; a crane controller is shown at the St. Louis World's Fair.
- 1909: The company is renamed Allen-Bradley.
- 1985: Rockwell International acquires Allen-Bradley.
- 2001: Rockwell Automation becomes the company's name; the Allen-Bradley brand marks 100 years in 2003.
Reading Allen-Bradley catalogue numbers
The first digits of an Allen-Bradley catalogue number identify the platform, which tells you what is compatible with what. 1756 is ControlLogix (chassis-based, used for large process and plant control), 1769 is CompactLogix 5370 with Compact I/O, 5069 is CompactLogix 5380 with Compact 5000 I/O, 1734 is POINT I/O, 1794 and 5094 are FLEX and FLEX 5000 distributed I/O, 1746 and 1747 belong to the older SLC 500 family, 1766 is MicroLogix 1400 and 2080 is Micro800. For drives, 25B is PowerFlex 525 and 22B is PowerFlex 40; in a code such as 25B-D010N114, "D" means 380–480 V, "010" is the output current rating, and N114 instead of N104 means the drive has an integrated EMC filter. Many plants in the region still run SLC 500 and older MicroLogix systems, which Rockwell has discontinued, so exact spares and migration to CompactLogix are both common requests.
Where Allen-Bradley products are used
In Oman and the GCC, Allen-Bradley controllers and drives run on oil and gas facilities, water treatment and pumping stations, cement, food and beverage and packaging plants, and on machines supplied by American OEMs. ControlLogix is often the platform for plant control systems, while PowerFlex drives are used on pumps, fans and conveyors.
Allen-Bradley products we list
| Family | Examples |
|---|---|
| ControlLogix | 1756-L85E, 1756-EN2T, 1756-EN2TR, 1756-IF16, 1756-IB32, 1756-PA75, 1756-A10 |
| CompactLogix and Micro controllers | 5069-L320ER, 5069-L340ERM, 1769-L33ER, 1769-L16ER, MicroLogix 1400, Micro820, SLC 500 (1746) |
| Distributed I/O | 1734-AENTR, 1734-IB8, 1734-IE2C, 1734-IB8S safety, 1794-AENTR, 5094-AENTR, 5069-IF8 |
| Operator terminals | PanelView Plus 7 10-inch, PanelView Plus 7 15-inch, PanelView 800, PanelView 5310 |
| Drives, motor control and networking | PowerFlex 525, PowerFlex 755, PowerFlex 4, 150-A180NBD SMC, Stratix 2000, 1783-NATR |
Ordering Allen-Bradley products: what we need
Send the full catalogue number and the series letter from the label (for example 1756-EN2T Series D), because firmware and compatibility can change between series. For drives, add the motor power, voltage and filter option. For a discontinued SLC 500 or MicroLogix part, tell us whether you need the exact spare or a migration proposal.
Facts checked against Rockwell Automation's published company history, October 2026.
Browse Allen-Bradley products by category: PLC & I/O Cards, AC Drives.
FAQ
Questions about the Allen-Bradley 440R-N23135 MSR127RP Safety Relay 24V
Answers from our engineering team on installation, compatibility and integration.
01What is 440R-N23135?
A 24V AC/DC MSR127RP safety relay with 3 N.O. safety outputs, 1 N.C. auxiliary output and manual monitored reset.
02What safety level is stated?
PLe Category 4 and SIL CL 3, with PFH 1.94E-09 per hour.
03How wide is it?
22.5 mm on a 35 mm DIN rail.
04Can it be repaired?
No, MSR127 relays are not repairable and must be replaced.
05What is the response time?
15 ms.
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