A transmitter includes a transmitter control section, which generates transmission data to be transmitted to a receiver. The transmission data contains variable data and verification data. The verification data is data for causing a verifying section of the receiver to verify an ID code registered in the transmitter against an ID code registered in the receiver. The transmitter control section is capable of switching between a first state and a second state. The first state is a state in which fixed data representing identification information is transmitted as the verification data. The second state is a state in which computation data computed from the variable data and the fixed data is transmitted as the verification data.