Aiming for marathon success The marathon function of ONYX Pro enables a runner to accurately check and evaluate the heart rate and split times during a marathon. ONYX Heart Rate Monitor - What's new? the digitally coded range from Sigma Sport® DIGICODE – Interference-free transmission! All models with digicode feature digitally coded transmission.		DIGICODE – Interference-free transmission! All new models with DIGICODE feature digitally coded wireless transmission. This transmission method eliminates disturbances during group training and prevents cross talk. Prior to each use, the digitally coded chest strap and heart rate monitor must be synchronized. As a result, the watch only receives data from it's own synchronized chest belt. The heart rate readings are converted into digital data packages and transmitted to the receiver within the monitor. A check sum guarantees that the digital data packages are correct. In addition, the "time coding & ID procedure" guarantees that data transmission is significantly more secure and accurate compared to analogue heart rate monitors.