This signal is used to indicate whether a modem is connected to a working phone line and a data carrier signal is detected. 此信号用于指示是否调制解调器已连接到正常工作的电话线并检测到数据载波信号。
Radio communication superimposes this information bearing signal onto a carrier signal. 无线电通信像素这一信息轴承信号上的载波信号。