Specifications

SIM900 AT Commands Set
SIM900_ATC_V1.01 195 23.06.2010
“AT+CCWA=1,1” before running this
demonstration.
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
waiting status), place active call on hold
and switch to incoming call. Switch
between both calls, placing each in the
hold state whilst the other is active
before terminating each one. This feature
relies on knowing each call’s ID. This is
done using the List Current
Calls(AT+CLCC) Command. A call’s ID
is required to switch between held and
active calls. Held calls that are not
automatically resumed when all other
calls are terminated. They need to be
made active using the AT+CHLD=2x
Command. Note call waiting must have
been previously enabled for this
demonstration to work.
ATD6241xxxx;
<RX incoming call>
AT+CHLD=2
AT+CHLD=21
AT+CLCC
AT+CHLD=22
AT+CHLD=12
AT+CHLD=11
OK
+CCWA: "1391818
6089",129,1,""
OK
<incoming call activated,
original on hold>
OK
<original call actived,
incoming call held>
+CLCC:1,0,0,0,0,"62
418148",129,""
+CLCC:2,1,1,0,0, "139
18186089",129, ""
OK
< Note incoming call held
flag set>
OK
<original call held, incoming
call active>
OK
<terminate incoming call>
<terminate original call>
Send busy status to incoming waiting
caller.
Establish a voice call from EVB, receive
an incoming call (incoming call accepts
waiting status), send ‘busy’ status to
waiting mobile. Note call waiting must
ATD6241xxxx;
<RX incoming call>
AT+CHLD=0
OK
+CCWA: "1391818
6089",129,1,""
OK
OK