> 9.8 | AT+CHLD Call Hold and Multiparty

> Syntax

> Test Command AT+CHLD=?
> Response(s)
> +CHLD: (list of supported <n>s)
> OK

> Write Command AT+CHLD=[<n>]
> Response(s)
> OK
> ERROR
> +CME ERROR: <err>

> Reference(s) |  | PIN |  | ASC0 | ASC1 | USB | MUX1 | MUX2 | MUX3 |  |  | Charge | Q | Last
> GSM 07.07 |  | + |  | + | + | + | + | + | + |  |  | - | - | -

> Command Description
> TA controls the Supplementary Services Call Hold and Multiparty. Calls can be put on hold, recovered, released, and added to a conversation.
> Like for all Supplementary Services, the availability and detailed functionality of Call Hold and Multiparty services depends on the configuration of the GSM network. The TC65 can only request the service, but the network decides whether and how the request will be answered.
> Parameter Description

> <n>(num)

> 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 or fax 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, data or fax call. If the waiting call is a data or fax call, it is also possible to put the voice call on hold. To switch back from the active data or fax 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.

> Example

> ^SYSSTART
> at+cpin="9999"
> OK
> +CREG: 2
> +CREG: 1,"0145","0016" | The mobile is now registered.
> at+ccwa=1,1,1 | You activate the indication of waiting calls during voice calls.
> OK
> atd"1234567"; | You make a voice call.
> OK
> +CCWA: "+491791292364",145,32,,0 | You receive a URC indicating a waiting data call.
> at+chld=2 | You put the voice call on hold.
> CONNECT 9600/RLP | The data connection is set up.
> hello
> +++ | With ''+++'' you go in command mode.
> OK
> at+clcc | You interrogate the status of all established calls.
> +CLCC: 1,0,1,0,0,"03038639268",129
> +CLCC: 2,1,0,1,0,"+491791292364",145
> OK
> at+chld=1 | The active data call is terminated and the held voice call becomes active.
> OK
> at+clcc
> +CLCC: 1,0,0,0,0,"03038639268",129
> OK