Abstract: A signal processing method includes: fetching an encrypted identifier of a controlled apparatus; filling the encrypted identifier into a device identification field of a data format of a control signal; generating an encrypted time code according to system time and an adjusting code of a controlling apparatus; filling the encrypted time code into a time identification field of the data format; generating a control signal having both device identification field and time identification field; receiving the control signal and fetching both device identification field and time identification field; comparing the device identification field with a predetermined device identification field; comparing the time identification field with the predetermined time identification field if the device identification field is equal to the predetermined device identification field; and executing an operation corresponsive to the control signal by the controlled apparatus if the time identification field is greater than the pre