Radionics

Tiller observes that pendulums, dowsing rods and radionics devices all serve to reduce the signal/noise ratio. They help the average individual who is not blessed with the gifts of concentration that are apparently inherent in gifted healers […]

But it's also because the Cambridge is British made by Sinclair Radionics Ltd, Europe's largest calculator manufacturer, with all the cost advantages of scale that this entails.