Track Occupancy sensor (Trackside Cabinet)

2020. Changed the description to "Track Occupancy sensor"
and added the Reed switch version of the short hall holder.
This appears to have greater sensitivity than the standard hall,and is not sensitive to the way up of the magnet on the train.

The Reed switch is a RI-80 1.8x5mm type,(supposedly 5-15AT sensitivity) mounted in line with the track for best sensitivity. It will switch when the magnet is a longer distance away than with the hall, but will switch off when the magnet is directl