Cartoon illustrating the model for the central engine of radio-quiet AGNs and radio-loud AGNs. Solid black lines represent the theoretically predicted correlation coefficients for ADAF, jet, and standard thin disc models, which are same as Figs. 4 and 5. The upper colored arrow represents the observational results for radio-quiet (RQ) AGNs, while the lower colored arrow represents the observational results for radio-loud (RL) AGNs. The different colors of the arrow represent different Eddington ratios (λ_Edd) and the direction of the arrow means from low λ_Edd to high λ_Edd. The shaded violet regions represent the origins of X-ray emission. The origins of X-ray emission of radio-quiet AGNs at 0.01 < λ_Edd < 0.1 are consistent with a combination of ADAF and a synchrotron jet model (ADAF+jet model), while at 0.1 < λ_Edd < 1, they mainly follow the synchrotron jet model (Jet model). The origins of X-ray emission of radio-loud AGNs are consistent with a combination of ADAF and a synchrotron jet model (ADAF+jet model) at λ_Edd < 0.01, and agree with the synchrotron jet model (Jet model) at 0.01 < λ_Edd < 0.1, and follow the standard thin disc coupled with a synchrotron jet model (Disc+jet model) at λ_Edd > 0.1.