It depends on whether the motorization is electric or combustion.Electric Models:Almost all ESC brands and models (except the Kontronik) have a special output for the motor rotation impulses that just need to be connected directly to the iKON2 “GOV” input connector.For those who have old ESCs without the output or use inexpensive ESCs without the motor rotation pulse output, a large number of sensors are available on the market that can detect the pluses output by the ESC and convert them to a format that is readable by the iKON2 unit.Special attention should be paid to some sensors (such as Eagle Tree) where the type of connector must be changed from JST to Futaba / JR, and have the red wire that corresponds to the ground/negative and the black wire that corresponds to the positive.Combustion models:Combustion models involve the use of magnetic sensors with magnets that must be glued to the cooling fan (in this case before the clutch) or to the main gear (in this case after the clutch) and the sensor must be fixed to the mechanics of the model by placing it at a very small distance from the travel path of the magnets (usually two sheets of paper are placed between the magnet and the sensor to set the correct gap between the sensor to the model).In this case, pay attention to some types of sensors, such as Align, that have the red wire that corresponds to the ground/negative and the black wire that corresponds to the positive reversed.For nitro models, there are the “backplate” sensors installed on the bottom of the engines. They do not work, however, with some engine that have a non-magnetic material connecting rod (for example some YS engines), moreover often it is necessary to find the correct position using spacer washers for correct readings and may prevent you from feeling the backplate with your finger to determine whether the engine is running lean or rich.