The system comprising a slave module and a master module. The master module comprises a master control module (CONTRM). The slave module comprises a determination module (DETER). The determination module (DETER) is configured to determine a value of a physical quantity of the slave module. The determination module (DETER) is configured to receive, from the master control module (CONTRM), a command to start counting and a command to end counting. The determination module (DETER) is configured to determine a number of oscillations, between reception of the command to start counting and reception of the command to end counting, of an oscillating signal of which a frequency depends on the value of the physical quantity.