Method carried out in system including active stylus and sensor controller, sensor controller, and active stylus

A sensor controller comprising:

• a transmitter configured to transmit an uplink signal including a first partial signal and a second partial signal;
• wherein the transmitter transmits the first partial signal by direct spreading using a first spread code and transmits the second partial signal by direct spreading using a second spread code, the second spread code being different from the first spread code and having a code length that is shorter than a code length of the first spread code;
• and
• a receiver configured to receive a downlink signal.

An active stylus comprising:

• a receiver configured to receive an uplink signal including a first partial signal and a second partial signal;
• wherein the receiver is synchronized with the uplink signal by detecting the first partial signal using a first spread code and thereafter detects the second partial signal using a second spread code, the second spread code being different from the first spread code and having a code length that is shorter than a code length of the first spread code;
• and
• a transmitter configured to transmit a downlink signal.