>The core layer can call the functions of the interface layer and uses the hook to call functions of the adaptation layer. In this way, the adaptation layer can indirectly call the functions of the interface layer, but the interface layer cannot call the functions of the adaptation layer.
**Figure 1** Unified service mode<aname="fig14423182615525"></a>
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@@ -284,7 +284,7 @@ The DAC module adaptation procedure is as follows: