(A) ;2-GUANIDINOTHIAZOLE DERIVATIVE

摘要

Method and apparatus for use with a magnetic tape playback machine to attenuate recorded audio signals relative to the super-imposed control signals while the magnetic tape is being transported past the sensing surface of a playback head. The control signals are recorded in a frequency range which is lower than the frequency range of the recorded audio signals. A spacer is attached to the sensing surface of the playback head to space the magnetic tape a preselected distance from the sensing surface and thereby attenuate the higher frequency audio signals relative the lower frequency control signals. The higher frequency attenuation obtained is independent of the frequency of the signals induced into the playback head and is thereby independent of the linear velocity of the magnetic tape as it is transported past the sensing surface of the playback head. The relatively unattenuated control signals may be obtained during fast forward or rewind of the magnetic tape playback machine and used to quickly regain synchronization between a visual image projector and an associated magnetic tape playback machine when one has been operated out of synchronization with respect to the other.