Sigma R3 Speed / Distance / Heart Rate Transmitter - BlackSigma R3 Speed Distance Heart Rate Transmitter Black The R3 transmitter enables you to measure your speed, distance and heart rate in a single device. The SIGMA STS Run wireless technology sends digitally coded data packages to the receiver within the running computer. All in One SPEED DISTANCE HEART RATE The R3 transmitter uses an integrated three axis acceleration sensor to measure acceleration throughout the run and accurately measure speed and