Asterisk Local Channels

In Asterisk, Local channels are a method used to treat an extension in the dialplan as if it were an external device. In essense, Asterisk will send the call back into the dialplan as the destination of the call, versus sending the call to a device.
Two of the most common areas where Local channels are used include members configured for queues, and in use with callfiles. There are also other uses where you want to ring two destinations, but with different information, such as different callerID for each outgoing request.

Delay Dialing Devices Example

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• Added by Malcolm Davenport, last edited by Malcolm Davenport on Aug 31, 2010

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Lets say when someone calls extension 201, we want to ring both the desk phone and their cellphone at the same time, but we want to wait about 6 seconds to start dialing the cellphone. This is useful in a situation when someone might be sitting at their desk, but don't want both devices ringing at the same time, but also doesn't want to wait for the full ring cycle to execute on their desk phone before rolling over to their cellphone.
The dialplan for this would look something like the following:

[devices] exten => 201,1,Verbose(2,Call desk phone and cellphone but with delay) exten => 201,n,Dial(Local/deskphone-201@extensions&Local/cellphone-201@extensions,30) exten => 201,n,Voicemail(201@default,${IF($[${DIALSTATUS} = BUSY]?b:u)}) exten => 201,n,Hangup() [extensions] ; Dial the desk phone exten => deskphone-201,1,Verbose(2,Dialing desk phone of extension 201) exten => deskphone-201,n,Dial(SIP/0004f2040001) ; SIP device with MAC address                                                 ; of 0004f2040001 ; Dial the cellphone exten => cellphone-201,1,Verbose(2,Dialing cellphone of extension 201) exten => cellphone-201,n,Verbose(2,-- Waiting 6 seconds before dialing) exten => cellphone-201,n,Wait(6) exten => cellphone-201,n,Dial(DAHDI/g0/14165551212)

When someone dials extension 201 in the [devices] context, it will execute the Dial() application, and call two Local channels at the same time:

Local/deskphone-201@extensions
Local/cellphone-201@extensions

It will then ring both of those extensions for 30 seconds before rolling over to the Voicemail() application and playing the appropriate voicemail recording depending on whether the ${DIALSTATUS} variable returned BUSY or not.
When reaching the deskphone-201 extension, we execute the Dial() application which calls the SIP device configured as '0004f204001' (the MAC address of the device). When reaching the cellphone-201 extension, we dial the cellphone via the DAHDI channel using group zero (g0) and dialing phone number 1-416-555-1212.

Dialing Destinations with Different Information

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• Added by Malcolm Davenport, last edited by Malcolm Davenport on Aug 31, 2010

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With Asterisk, we can place a call to multiple destinations by separating the technology/destination pair with an ampersand (&). For example, the following Dial() line would ring two separate destinations for 30 seconds:

exten => 201,1,Dial(SIP/0004f2040001&DAHDI/g0/14165551212,30)

That line would dial both the SIP/0004f2040001 device (likely a SIP device on the network) and dial the phone number 1-416-555-1212 via a DAHDI interface. In our example though, we would be sending the same callerID information to both end points, but perhaps we want to send a different callerID to one of the destinations?
We can send different callerIDs to each of the destinations if we want by using the Local channel. The following example shows how this is possible because we would Dial() two different Local channels from our top level Dial(), and that would then execute some dialplan before sending the call off to the final destinations.

[devices] exten => 201,1,NoOp() exten => 201,n,Dial(Local/201@internal&Local/201@external,30) exten => 201,n,Voicemail(201@default,${IF($[${DIALSTATUS} = BUSY]?b:u)}) exten => 201,n,Hangup() [internal] exten => 201,1,Verbose(2,Placing internal call for extension 201) exten => 201,n,Set(CALLERID(name)=From Sales) exten => 201,n,Dial(SIP/0004f2040001,30) [external] exten => 201,1,Verbose(2,Placing external call for extension 201) exten => 201,n,Set(CALLERID(name)=Acme Cleaning) exten => 201,n,Dial(DAHDI/g0/14165551212)

With the dialplan above, we've sent two different callerIDs to the destinations:

• "From Sales" was sent to the local device SIP/0004f2040001
• "Acme Cleaning" was sent to the remote number 1-416-555-1212 via DAHDI

Because each of the channels is independent from the other, you could perform any other call manipulation you need. Perhaps the 1-416-555-1212 number is a cell phone and you know you can only ring that device for 18 seconds before the voicemail would pick up. You could then limit the length of time the external number is dialed, but still allow the internal device to be dialed for a longer period of time.

Fuente :
https://wiki.asterisk.org/wiki/display/AST/Local+Channel