If you change without interruption (e.g. stop overs that take less than 20-30 minutes) from one line to another, you will not be required to check-out. FAIRTIQ will recognise that you changed line and calculate the optimal fare.
For longer interruptions we recomend a temporary check-out. Before re-entereing the means of transport you have to check-in again. This has no influence on the calculation of the price. The system calculates automatically all journeys and computes the cheapest ticket combination possible.