The APC's receiver protects the train power supply when travelling through neutral sections in the overhead line. The receiver interacts with magnets placed outside the track at the beginning and end of the neutral zone. Traditionally, the APC receiver was not solid state and worked using relays, which are now obsolete. Unipart Rail's ability to look at existing products and improve them interested Transportations Systems. The initial product discussions focussed on AWS developments, in particular how Unipart Rail had taken the non-electronic version and produced a successful solid-state version ,now used throughout the world by train operators.