Coupling relays and signal converters

When standard controllers with their standard inputs/outputs reach their limits, coupling relays and signal converters come into their own. A wide selection of coupling relays and signal converters are available for the electrical isolation of I/Os and PLC inputs and outputs, signal amplification or reproduction, as well as conversion to different voltage levels or signal forms. We offer the appropriate solution for all requirements.

Technical specifications for coupling relays and signal converters

Industry Mall

Depending on your requirements, we offer you different coupling relays and signal converters

3RQ1 Coupling Relays

Force-guided coupling relays up to SIL 3 / PL e

SIRIUS 3RQ1 coupling relays force-guided with functional safety up to SIL 3 / PL e

With the 3RQ1 coupling relays fail-safe controls can be reliably coupled. They are available in widths of 17.5 or 22.5 mm. Because the relays are force-guided in accordance with IEC 60947-5-1 (IEC 61810-3), the mechanical connection between the contacts ensures the NO and NC contacts are never closed simultaneously. This means failures to open can be reliably recognized in order to ensure maximum safety. This makes them suitable for use in rail, signal systems, and elevators, for example.


These coupling relays are also an integral component of the 3SK safety relay system, and serve as an output expansion up to SIL 3.


  • Wide voltage ranges from 24 to 240 V AC/DC with a mounting depth of 90 mm available for all variants
  • Permanent wiring due to removable terminals in screw and spring-type technology (push-in)
  • Force-guided contacts used to read back relay status values and provide reliable diagnostics or signaling
  • All variants with genuine load contacts, including in NC circuit
  • Usable as an output expansion for SIRIUS 3SK safety relays via a device connector
  • Safety certification based on functional safety up to SIL 3 / PL e (IEC 61508 / ISO 13849)

3RQ2 coupling relays

Universal with wide voltage range

SIRIUS 3RQ2 coupling relays with wide voltage range for universal use

The SIRIUS 3RQ2 coupling relays in high-quality titanium gray industrial enclosure ensure a convenient connection system with removable terminals. Outstanding features also include a wide range supply voltage of 24 to 240 V AC/DC for global use.


  • One product for all voltages (24 to 240 V AC/DC) with 1 to 3 changeover contacts
  • Version with hard gold-plated contacts for maximum contact reliability, even at low currents
  • International standards and certifications include CE, UL/CSA, EAC, CCC and confirmations for railway applications

3RQ3 coupling relays

Compact with relay and semiconductor output

SIRIUS 3RQ3 coupling relays for space-optimized use in the control cabinet

The SIRIUS 3RQ3 coupling relays with a width of just 6.2 mm and low overall depth/height are ideal for narrow tier spacing or in flat switchboxes. They are available with either relay or semiconductor output.


  • Permanently soldered relays for enhanced contact reliability
  • Plug-in relays to ensure quick replacement of the relays with permanent wiring
  • Semiconductor output for an extremely long electrical service life with an unlimited number of switching cycles
  • Universal bridging option using connecting combs for all terminals

LZS coupling relays

Powerful with plug-in relays

SIRIUS LZS coupling relays with plug-in relays

SIRIUS LZS coupling relays are available both as complete units, as individual modules for customer assembly, or for spare parts requirements. These are characterized by increased power for the switching of greater loads.


The plug-in relays allow quick replacement of the relays.


  • Tested AC-15 and DC-13 switching capacity
  • Available coil voltages: 24 V DC, 24 V AC, 115 V AC, 230 V AC
  • Hard gold-plated contacts for optimum interaction with electronic controls

3RS70 signal converters

For analog standard and universal signals

SIRIUS 3RS70 signal converters in narrow compact design

3RS70 signal converters are mainly used to electrically isolate and convert analog signals. The frequency outputs implemented offer a further application. Only minimal space required on the standard mounting rail due to the narrow design of just 6.2 mm and reduced depth and height of the enclosure, ideal for flat switchboxes and control cabinets with small gaps between tiers.


Reduced device variance resulting from exclusive use of 3-way separation. For the 3-way separation, each circuit is galvanically separated from the other circuits, i.e. input, output, and supply voltage do not have equipotential bonding.

3TG10 power relays

For performance range below S00

Compact SIRIUS 3TG10 power relays for switching of high loads

3TG10 power relays are the ideal option wherever small, low-noise relays or contactors are required. They are suitable for simple controllers and for applications that do not require an overload relay and need only one auxiliary switch – but which therefore need more switching power, higher switching voltage, and a longer service life.


  • Can be mounted in any position, hum-free
  • Narrow width of just 36 mm
  • Integrated auxiliary switch
  • Protective separation
  • Integrated overvoltage damping

Stay up to date

Visit our Reference Library

Check out our how-to videos, customer references & solutions briefs that can help you solve your challenges.