A sensor controller includes a transmitter configured to transmit an uplink signal including a first partial signal and a second partial signal. The transmitter is configured to transmit the first partial signal by direct spreading using a first spread code and transmit the second partial signal by direct spreading using a second spread code which is different from the first spread code and which has an identical chip time length to the first spread code. An active stylus includes a receiver configured to receive an uplink signal including a first partial signal and a second partial signal. The receiver is configured to synchronize with the uplink signal by detecting the first partial signal using a first spread code and thereafter detect the second partial signal using a second spread code, which is different from the first spread code and has an identical chip time length to the first spread code.