S.BUS2 input and output previous system (ch1-4); Dimensions: 0.7 x 1.6 x 0.3 inches (18.0 x 41.4 x 9.9 mm); Weight: 0.1 oz (4.8 g); Frequency: 2.4 GHz-T-FHSS AIR ; Power supply: 4.8 - 7.4 V (batteries cannot be used); Standard connector). Each transmitter model data has a unique ID number (Model ID) The receiver will not activate unless the model data matches the memory ID. Prevents misoperation due to mis-operation of model selection