# Smart AT, switched


The following chart describes what DTR does for smart AT switched mode of operation. The rows present the possible operating modes, and the columns describe the modem Data Terminal Detect (DTD) operation for the four supported &D commands. Refer to the previous section for definitions of the modem behaviors. 
Operating Mode     &D0    	   &D1    	      &D2    	      &D3   

V.14 (&Q0) 		  none        E           I, H           R        

&Q1        		 C, H        C, E         I, C, H      C, R     

&Q2        	   I, D ,H 	   I, D, H 	  I, D, H     I, D, R 

&Q3              I, O, H  	   I, O, H      I, O, H     I, O, R  

AutoSync(&Q?)     	H          E          I, H          R        

AutoSync II(&Q?)   none         E          I, H          R        

error control(&Q?) none         E          I, S          R        

ASB(&Q?)   		  none         E          I, S          R
Click here to return to the &Dn - Select Data Terminal Ready Option page.

Click here to return to the Contents page.