with standard adsl activation initialization and showtime signals and is transmitted at a level high enough to mask the crosstalk signals for the adsl system illustrated in fig1 it is convenient to employ a medley signal as the crosstalk masking signal medley is an aperiodic sequence that is also employed during normal adsl link initialization when used without a pilot tone or cyclic prefix the medley signal is a good approximation of a broadband random signal continuing the example described with reference to fig1 the first atu c 106 a transmits a valid adsl downstream signal potentially including pilot tone at a nominal power level of u2212 40 dbm hz as previously described the second atu r 108 b detects the downstream signal from the first atu c 106 a in the form of crosstalk 110 the coupling loss associated with the crosstalk 110 is 70 db thus the second atu r 108 b receives the downstream signal from the first atu c 106 a at a power level of approximately u2212 110 dbm hz which is similar to the level that it would expect from a valid atu c on a long loop however in accordance with the present embodiment a masking signal is transmitted from the second atu c 108 a to the second atu r 108 b assuming worst case crosstalk levels of 60 70 db below nominal transmitter levels the masking signal is sent at transmit power spectral density psd levels 30 40 db below nominal transmit levels typically transmitting the mask at such a power level is sufficient to mask the crosstalk signals 110 at the second atu r 108 b and.