In one embodiment, a system comprises a touch sensor and a stylus. The touch sensor comprises drive lines and sense lines arranged such that intersections of the drive lines and sense lines form capacitive nodes. The drive lines transmits a first signal having an identification portion. The stylus comprises a sense unit and a drive unit. The sense unit senses the first signal from the drive lines, compares the identification portion to criteria stored in the stylus, and authorizes the drive unit to transmit a second signal based on the first signal if the identification portion satisfies the criteria stored in the stylus. The drive unit transmits the second signal to the sense lines such that transmission of the second signal changes capacitance of the capacitive nodes.
