After Market Relays

UMD-U300 relay - Voltage monitoring, AC input



Plug-in electronic voltage monitoring relay with one change-over contact and one normally open contact, suitable for AC voltages with a frequency of 50/60 Hz. The pull-in voltage is adjustable with a lockable knob. The relay can also be supplied with a fixed pull-in voltage (no knob). The UMD-U300 offers a small hysteresis (difference between pull-in and drop-out voltage) and does not need an auxiliary supply.
The relay is equipped with two LEDs which indicate the presence of power supply and contact switching.
The construction of the relay and choice of materials makes the UMD-U300 relay suitable to withstand low and high temperatures, shock & vibrating and dry to humid environments. No external retaining clip needed as integrated ‘snap-lock’ will hold relay into socket under all circumstances and mounting directions.
Compact design, choice of many options and a wide range of sockets makes the UMD-U300 relay an easy and flexible solution to use.


These relay series are designed for demanding train borne applications. The UMD-U300 is used in applications for voltage monitoring or where switching is activated by a fixed voltage level.


  • Voltage monitoring relay
  • AC input
  • 1 C/O contact and 1 N/O contact
  • Fixed pull-in and drop-out voltage
  • Small hysteresis
  • No auxiliary supply necessary
  • Two LEDs for status indication
  • Flat, square and silver plated relay pins for excellent socket connection
  • Integrated snap lock
  • Optional positive mechanical keying relay to socket


  • Proven reliable
  • Long term availability
  • Easy to maintain
  • Low life cycle cost
  • No maintenance

Railway compliancy

  • EN 50155 Electronic equipment used on rolling stock for railway applications
  • IEC 60571 Electronic equipment used on railway vehicles
  • IEC 60077 Electrical equipment for rolling stock in railway applications
  • IEC 60947 Low voltage switch gear and control gear
  • IEC 61373 Rolling stock equipment - Shock and vibration test
  • IEC 60947-5-4 Electromechanical components for control applications. This standard examines both coil and contact specifications in depth
  • EN 50121 Electromagnetic compatibility for railway applications
  • NF F 16-101/102, TS 45545-2 Fire behaviour - Railway rolling stock
  • NF F 62-002 On-off contact relays and fixed connections



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Railway rolling stock
Railway signalling