US Patent 7821420 Signal transmission system for a measurement device

A transmission system for a measurement device on a coordinate positioning apparatus comprises a station (18) mounted on the measuring device (10) and a station (20) mounted on the coordinate positioning apparatus (22), wherein the stations communicate with each other using a spread spectrum radio link, for example frequency hopping. The station on the probe sends a regular signal and on receiving the signal the station on the coordinate positioning apparatus synchronises its clock and sends an acknowledgement signal. Measurement data is either sent in the regular signal or in a measurement event driven signal.