This process is carried out by safety-critical centrally located computers, called "evaluators", with the axle counter sensors located at the required sites in the field. The axle counter sensors are either connected to the evaluator via dedicated copper cable or via a telecommunications transmission system. That allows the axle counter sensors to be located a significant distance from the evaluator, and is useful when using centralised interlocking equipment, but less so when signalling equipment is situated beside the line in equipment cabinets.