A pen is configured to supply an N-bit internal digital value NA to a sensor device, and includes an integrated circuit that acquires a series of the internal digital values NA(s) based on a state OPS of a writing pressure detector. The integrated circuit supplies a first internal digital value NA to the sensor device by transmitting, from an antenna, first transmission data MF including a first standard digital value MS corresponding to the first internal digital value NA. The integrated circuit supplies a second internal digital value NA to the sensor device by transmitting, from the antenna, second transmission data MF that is smaller than N bits and includes an M-bit relative digital value (M