Specifications

SIM900 AT Commands Set
SIM900_ATC_V1.01 58 23.06.2010
Parameter
<type> type of address octet in integer format;
129 Unknown type(IDSN format number)
161 National number type(IDSN format)
145 International number type(ISDN format )
177 Network specific number(ISDN format)
Reference
GSM 07.07 [13]
Note
The ATD Command overrides this setting when a number is dialed.
3.2.14 AT+CHLD Call Hold and Multiparty
AT+CHLD Call Hold and Multiparty
Test Command
AT+CHLD=?
Response
+CHLD: (list of supported <n>s)
OK
Write Command
AT+CHLD=<n>
Response
TA controls the supplementary services Call Hold, Multiparty and Explicit
Call Transfer. Calls can be put on hold, recovered, released, added to
conversation, and transferred.
Note These supplementary services are only applicable to tele service 11
(Speech: Telephony).
OK
If error is related to ME functionality:
+CME ERROR: <err>