Specifications

TC35i AT Command Set
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TC35i_ATC_V01.05 Page 93 of 278 04.08.2003
4.16 AT+CHLD Call hold and multiparty
Test command
AT+CHLD=?
Response
+CHLD: (list of supported <n>s)
OK
Write command
AT+CHLD=[<n>]
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.
Response
OK
If error is related to ME functionality:
+CME ERROR: <err>
Parameter
<n> 0 Terminate all held calls; or set UDUB (User Determined User
Busy) for a waiting call, i.e. reject the waiting call.
1 Terminate all active calls (if any) and accept the other call
(waiting call or held call)
1X Terminate the active call X (X= 1-7)
2 Place all active calls on hold (if any) and accept the other call
(waiting call or held call) as the active call
2X Place all active calls except call X (X= 1-7) on hold
3 Add the held call to the active calls
Reference
GSM 07.07
Note
· The AT+CHLD command offers a broad range of options according to the
GSM specifications. However, many of these options are dependent on the
SIM card / service provider. If you attempt to invoke an option which is not
provisioned by the network, or not subscribed to, invocation of this option will
fail. The responses in these cases may vary with the network (for example
“Operation not allowed”, “Operation not supported” etc.).
· The supplementary service is only applicable to teleservice 11 (Speech te-
lephony). AT+CHLD can be used to both accept a waiting voice call and put
an active voice call on hold.
A data or fax call, however, cannot be put on hold. But it is possible to place a
voice call on hold in order to accept a waiting data or fax call, and afterwards
to recover the voice call. In this case, the only difference over speech teleph-
ony is that AT+CHLD only puts the voice call on hold, the data or fax call need
to be manually accepted (via ATA).
Use the AT+CCWA command to activate the Call Waiting service. The
classes (bearer services) of waiting calls can be easily distinguished if the
URC +CCWA: <number>,<type>,<class>,,<CLI validity> is enabled.
For step-by-step instructions refer to the example below. A description of the
AT+CCWA command can be found in Chapter 4.9.
· The NO CARRIER result code is not displayed when a held call has been dis-
connected from either party. In order to get an indication of this disconnection,
please refer to AT+CSSN command (see Chapter 4.47).
· In conflicting situations, e.g. when a waiting call comes while there are already
held calls, the above procedures apply to the waiting call only. For example,
<n>=0 rejects the waiting call, but does not affect the held calls.
· The current states of all calls can be easily checked at any time by using the
AT+CLCC command. For details refer to Chapter 4.20.