Specifications
SIM900 AT Command Manual       
SIM900_AT Command Manual_V1.03  26  12/24/2010 
1.  No characters entered for T1 time (1 second) 
2.  "+++" characters entered with no characters in between (0.5 second) 
3.  No characters entered for T1 timer (0.5 second) 
4.  Switch to Command mode, otherwise go to step 1. 
Parameter 
Reference 
V.25ter 
Note 
To return from Command mode back to data mode: Enter ATO. 
2.2.13 ATO    Switch from Command Mode to Data Mode 
ATO Switch from Command Mode to Data Mode 
Response 
TA resumes the connection and switches back from Command mode to data 
mode. 
CONNECT 
If connection is not successfully resumed 
NO CARRIER 
else 
TA returns to data mode from Command mode CONNECT <text> Note: 
<text> only if parameter setting ATX>0 
Execution 
Command 
ATO[n] 
Parameter 
<n> 0 Switch from Command mode to data mode. 
Reference 
V.25ter 
Note 
2.2.14 ATP Select Pulse Dialling 
ATP Select Pulse Dialling 
Execution 
Command 
ATP 
Response 
OK 
Reference 
V.25ter 
Note 
No effect in GSM 
2.2.15 ATQ    Set Result Code Presentation Mode 
ATQ Set Result Code Presentation Mode 
Execution 
Command 
ATQ<n> 
Response 
This parameter setting determines whether or not the TA transmits any result 
code to the TE. Information text transmitted in response is not affected by 
this setting. 










