  The response of the level anti-crossing signal to a quasi-resonant
radio-frequency field, which appears in a zero magnetic field at NV color
centers in diamond, is investigated. It is shown that the complex structure of
this response can be explained by the Autler-Townes splitting. The possibility
of controlling the parameters of the level anti-crossing signal is considered.
It is shown that the slope of the central resonance recorded in this structure
upon low-frequency modulation of the external magnetic field can be 2.3 times
higher than the slope of the resonance recorded in the absence of an RF field.
Conclusions are drawn about the nature of the level anti-crossing effect
arising in zero field in NV color centers in diamond.
