At+Chld Call Hold And Multiparty - Multi-Tech MultiModem EDGE Reference Manual

9.8 AT+CHLD Call Hold and Multiparty

Description:
Test Command Syntax:
Response:
Write Command Syntax:
Response:
Parameter Descriptions:
<n>
0 Release all held calls or set User Determined User Busy (UDUB) for a waiting call:
•
If a call is waiting, release the waiting call. The calling party will receive a "BUSY" indication
(Supplementary Service User Determined User Busy "UDUB")
• Otherwise, terminate all held calls (if any).
1 Terminate all active calls (if any) and accept "the other call" as the active call:
•
If a call is waiting, the waiting call will be accepted.
• Otherwise, if a held call is present, the held call becomes active.
1X Terminate a specific call X (X= 1-7). The call may be active, held or waiting.
The remote party of the terminated call will receive a "NO CARRIER" indication.
Parameter X is the call number <idx> of the targeted call in the list of current calls available with
AT command AT+CLCC.
2 Place all active calls on hold (if any) and accept "the other call" as the active call:
•
If a call is waiting, the waiting call will be accepted.
•
Otherwise, if a held call is present, the held call becomes active.
2X Place all active calls except call X (X= 1-7) on hold. Parameter X is the call number <idx> of the
targeted call in the list of current calls available with AT command AT+CLCC.
3 Add a held call to the active calls in order to set up a conference (multiparty) call.
Notes:
• The AT+CHLD command offers a broad range of options according to the GSM specifications. However, 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 handling of the supplementary service Call hold and Multiparty varies with the types of calls. This is because
only voice calls can be put on hold, while data calls cannot. The following procedures apply:
With AT+CHLD=2 the user can simultaneously place a voice call on hold and accept another waiting voice or
data call. If the waiting call is a data call, it is also possible to put the voice call on hold. To switch back from the
active data call to the held voice call the active call must be terminated with AT+CHLD=1. If all active and held
calls are voice calls it is possible to switch back and forth with AT+CHLD=2.
•
In conflict 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.
•
See also the AT+CCWA command for details on how to display waiting calls.
See the Example on the next page.
Multi-Tech Systems, Inc. AT Commands for EDGE Modems (S000371G)
TA controls the Supplementary Services Call Hold and Multiparty. Calls can be put on
hold, recovered, released, and added to a conversation.
As for all Supplementary Services, the availability and detailed functionality of Call Hold
and Multiparty services depends on the configuration of the GSM network. The Multi-Tech
wireless modem can only request the service, but the network decides whether and how
the request will be answered.
AT+CHLD=?
+CHLD: (list of supported <n>s)
OK
AT+CHLD=[<n>]
OK
ERROR
+CME ERROR: <err>
Chapter 9 – Supplementary Service Commands
124