FM4-LO | Laser Optics

The FM4-LO contact wire measuring device is specially designed for static point measurement of contact wires. The laser beam of the FM4-LO determines the position of the catenary in relation to the track center as well as from the top of the rail.

This enables you to measure quickly and easily the:

  • Contact wire height and stagger (zig-zag)
  • Messenger wire height and stagger
  • Bridge and tunnel heights, height of crossing power lines
  • With accessories: Distance between pole leading edge and track center (FM4-LO Edge Configuration)
For use in light rail
For use in long-distance rail


  • Project planning and construction of overhead line systems
  • Regulatory and maintenance tasks on catenary and contact lines
  • Calibration and control and of continuous, dynamic geometry measurement methods
  • Optimized for flexible and mobile use in light and long-distance rail


In combination with the measuring bar, the measuring device can measure contact wire stagger on track gauges in the range of 750 - 1676 mm. The measurements can be performed quickly and in any weather condition.

High-precision laser measurement with up to 1.5 mm measuring accuracy 

Easy and fast detection of the contact wire by the target optics (crosshairs/laser beam)

Fast measurement due to easy and almost self-explanatory handling


Designed for construction site environments

  • Target optics with crosshairs for quickly catenary detection in daylight and including bright sunshine
  • Non-contact laser distance measurement of catenary height, visible red laser spot on the target surface
  • Single or continuous measurements as useful search function and for differentiation of the distances
  • Automatic display illumination, LED back lit for target optic, stagger scale illumination
  • Special protection against dust and water for use at almost any weather conditions
  • Minimal staffing expenses for logistics and measurements
  • Without affecting traction power supply through contactless measurements and insulated track contact
  • Contactless measurement (optic, laser); therewith no interruption of the current supply during the measurements in the corresponding track section necessary

Optional accessories

  • LED lighting device for measurements in the dark
  • Laser glasses for better visibility of the laser point
  • Carrying bags and power adapter for more comfort
  • Measuring bars for worldwide track gauges from 750 – 1676 mm
  • Edge configuration for distance measurement from the pole leading edge to the track center
    Catenary Contact Wire Measuring device LO

    Contact wire measuring device FM4-LO

    No. 785539:005.26 | Measurement of the height and stagger of contact wires by vertical laser beam and crosshair optics | approx. 26 x 11 x 10 cm
    Catenary Contace Wire Measuring device LO-MVK

    Contact wire measuring device FM4-LO-MVK

    No. 785539:010.26 | Measurement of the height and stagger of contact wires by vertical laser beam and crosshair optics, incl. mirror attachment for laser beam deflection to measure the distance between pole leading edge – track center | approx. 26 x 11 x 12 cm

    Instruction manual FM4-LO

    No. 785539:005.26.BA-E | Language English
    Transport Case

    Aluminum transport case for FM4-LO

    No. 99.53717 | For the transport of the measuring device, accessories and documents | approx. 54 x 16 x 25 cm / 3,3 kg
    Catenary Contact Wire Measuring bar

    Measuring bar standard

    No. 785532:051.26 | Adjusted to track gauge: 1435 mm or to another track gauge in the range: 750 - 1676 mm, measuring range ± 700 mm, scale value 1 mm, not separable | approx. 184 x 20 x 16 cm | approx. 4.7 kg
    Catenary Contact Wire Measuring bar seperable

    Measuring bar standard separable

    No. 785532:052.26 | Adjusted to track gauge: 1435 mm or to another track gauge in the range: 750 - 1676 mm, measuring range ± 700 mm, scale value 1 mm, separable (2 parts) for a flexible transport  | approx. 184 x 20 x 16 cm | approx. 5.1 kg
    Tragetasche für teilbare Messschienen

    Carrying bag for divisible measuring bars

    No. 99.53686 | Robust padded fabric bag, two carrying straps, adjustable shoulder strap |  approx. 105 × 28 × 18 cm
    Akku-Ladegerät UC20 (AAA)

    Battery charger UC20 (AAA)

    No. 99.74089 | Input 100-240 V (AC), incl. 4 diverse plug adapters for worldwide use and 2 pcs. AAA NiMH rechargeable batteries 800 mAh
    Laser Glasses

    Laser glasses

    No. 99.50968 | Improved visibility of the red laser point at daylight, sunlight or light reflections

    LED lighting device

    No. 785532:100.26 | LED lamp with clamp bracket for fixing on the measuring bar | for better visibility of the overhead lines at night or in tunnels

    Shipping packageBasicStandardEdge
    Length [cm]197110 110
    Width [cm]3737 37
    Height [cm]3737 37
    Weight [kg]1518 18