Data Sheet

SIM900 AT Commands Set
SIM900_ATC_V1.00 191 15.01.2010
ATA
ATH
OK[accept call]
OK[hang up call]
Call related supplementary service:
AT+CHLD. This Command provides
support for call waiting functionality.
AT+CHLD=<N>
<N>=0 RELEASE
ALL HELD CALLS
OR SEND USER
BUSY STATUS TO
WAITING CALL
<N>=1 RELEASE
ALL ACTIVE CALLS
AND ACCEPT
OTHER
CALL(WAITING OR
HELD) <N>=1X
RELEASE CALL X
<N>=2 PLACE ALL
ACTIVE CALLS ON
HOLD AND ACCEPT
CALL <N>=2X
PLACE ALL CALLS
ON HOLD EXCEPT
CALL X
Return value:(0,1,1x,2,2x,3)
Terminate current call and accept waiting
call.
Establish a voice call from EVB, receive
an incoming call(incoming call accepts
waiting status), terminate active call and
accept incoming call. Note call waiting
must be active for this option – use
“AT+CCWA=1,1” before running this
demonstration.
AT+CCWA=1,1
ATD6241xxxx;
<RX incoming call>
AT+CHLD=1
OK
OK
+CCWA:”62418148”,
129,1,””
OK
<waiting call active>
Set current call to busy and accept
waiting call.
Establish a voice call from EVB, receive
an incoming call(incoming call accepts
waiting status), place active call on hold
and switch to incoming call. Terminate
active call and switch back to original
call. Note call waiting must have been
previously enabled for this
demonstration to work.
ATD6241xxxx;
<RX incoming call>
AT+CHLD=2
AT+CHLD=1
+CCWA:”1391818
6089”,129,1,””
OK
<waiting call active other
call on hold>
OK
<incoming call terminated,
dialed number now active>
Switch between active and held calls.
Establish a voice call from EVB, receive
an incoming call (incoming call accepts
ATD6241xxxx;
<RX incoming call>
OK
+CCWA:”1391818