Abstract: An audio signal is divided into a plurality of bands prior to generating a shadow. The shadow is created by delaying the portion of the audio signal in at least one band by less than fifty milliseconds and combining the shadow signal with the portion of the audio signal. The portions, with any shadows, are combined to produce a reconstructed audio signal. The presence or absence of a shadow signal represents data or the data is represented by two or more shadow signals, in one or more bands. The period of delay of a portion in a band should not equal the period of the center frequency of that band. Preferably, the period of delay of a portion in a band does not equal the period of any frequency within the pass band.

Abstract: A system is provided for synchronizing a PSTN clock and a DSL clock. The system comprises a PSTN interface for transmitting and receiving voiceband samples, a data DSL transceiver for modulating and demodulating data to and from DSL samples, a synchronization circuit for synchronizing the voiceband samples and the data samples, and a converter for converting the synchronized voiceband and DSL samples between analog and digital formats. The synchronization circuit synchronizes the voiceband and the data samples for conversion by the same converter.