In this brief article we will explain how to implement Call Parking on FreeSwitch.

What is Call Parking?

Call parking is a feature in a telephone system that allows a call to be placed on hold and “parked” at a designated extension, where it can be retrieved by any phone within the system. This can be useful when a call needs to be transferred to someone who is not available at the moment, or when a call needs to be transferred to to yourself in a different room.

How FreeSwitch Implements Call Parking

You can use two functions,  valet_park() from  mod_valet_parking() or  park() from mod_dptools to implement call parking. 

Park() is very simple and just sends the call to a “limbo” where it can be retrieved using uuid_bridge or uuid_transfer.  You have to implement your own logic of parking. 

Valet_park() is more robust and implements the whole logic of call parking.

Valet park options:

<lotname> <extension>|[ask [<min>] [<max>] [<to>] [<prompt>]|auto [in|out] [min] [max]]

Parking a Call 

<extension name="park-in">
   <condition field="destination_number" expression="^(700)$">
      <action application="valet_park" data="{domain} auto in 701 799"/>
   </condition>
</extension>

Retrieving a Call

 <extension name="park-out">
  <condition field="destination_number" expression="^(7\d\d)$">
    <action application="answer"/>
    <action application="valet_park" data="{domain} $1"/>
  </condition>
</extension>

Using DTMF to park a call

During the call you can call *7 to park a call. The application bind_meta_app ties a DTMF number to a function. 

<action application="bind_meta_app" data="7 a s valet_park::{domain} auto in 701 799"/>

Announcement

The standard announcement is a bit rude. I want to change to “your call is parked at the extension <extension>

To change the phrase macros associated to valet parking you have to edit:

/etc/freeswitch/lang/en/vm/sounds.xml

You can change the the valet announce changing the phrase macro

valet_announce_ext
valet_lot_full
valet_lot_empty

Change valet_anounce_ext to 

<macro name="valet_announce_ext">
  <input pattern="^([^\:]+):(.*)$">
    <match>
      <action function="play-file" data="ivr/ivr-extension_number.wav"/>
      <action function="say" data="$2" method="pronounced" type="name_spelled"/>
    </match>
  </input>
</macro>

Reference

You can find more details on valet parking at:

https://developer.signalwire.com/freeswitch/FreeSWITCH-Explained/Modules/mod_valet_parking_3966447