In order to recover meaningful signal and error-free audio from a signal impaired by interference and fading, the receiver uses concatenated Reed-Solomon block coding and Forward Error Correction encoding and decoding (codec). This technique was proven in the early days of satellite modems in the late 1970s. Linkabit, then run by Irwin Jacobs prior to his involvement with Qualcomm, offered such a codec for rack mounting in satellite earth stations. The Sirius signal uses more robust error correction on control channels than on the audio content, trading off error correction and bandwidth differently for separate categories of bits in the signal waveform.