Electric Detector Boxes for Points

A variety of designs are available for use either with mechanically operated points, or in conjunction with our electric points machines.


  • Electrical detection of facing or trailing points
  • Variety of designs for different gauges and applications
  • Minimal maintenance required
  • Can be adjusted to suit any points throw


The position of the switch rails is transmitted to the detector box by adjustable rods attached to the switch rails, either directly, or via switch rail nose extensions. The detection is achieved by means of limit switches that are opened and closed by slides. There are two limit switches, one for each switch rail. The front contacts of one limit switch are normally wired in series with the back contacts of the other and vice versa. By this means one switch rail is detected as being closed against its stock rail and the switch rail as being open.

When an electric detector box is used with one of our electric point & lock machines it must be mounted on a special bolt-on alignment plate.


Apart from occasional checking of adjustment and track gauging these detector boxes are maintenance free. The special polymer slider bearings (where fitted) require no lubrication. The limit switches are rated at >10 million operations.

Several models are available. Please contact Signal Aspects Ltd for details and advice.

Every effort has been made to ensure that the information presented in this document is correct. Signal Aspects Ltd reserves the right to change any part of the specification without notice.

Information sheet
PDF file (242kB)