2101857-A is referenced by 35 patents.
A communications system for a device 10 incorporates a conductor 26 extending along a locus near to the device 10, and a transmitter 52 arranged to transmit signals through the conductor 26. The system also includes a receiver 55 at the device 10, arranged to detect the signals by capacitive means. The signals consist of two or more frequencies which are converted to corresponding voltage levels at the receiver 55. The device 10 may be a carriage driven alongside the conductor 26 by a motor receiving drive current from the conductor by inductive coupling.