It is not possible to use a trackle that has been used by someone else. Here is why: as a medical device that has to follow certain legal standards, we exclude the transfer of the sensor in order to exclude the risk of infection. We are aware that the sensors can be disinfected, but we do not recommend this; instead, we explicitly exclude the passing on in the operating instructions.

Apart from the risk of infection: if  we were to link the trackle with the account of another user, the data of two different users would be mixed up. This would render all calculations of the fertile period unusable, and the system could no longer be used as a contraceptive.