To Enable/Disable the DND (do not disturb) check/Uncheck the DND checkbox (1), to configure press the Right button (2), the DND dialog will be displayed.

VoxManager have two DND features, can manage through the asterisk dialplan or independently, the usefulness of using Asterisk is just for monitoring the DND state.

To extend this Feature to asterisk and monitor it, Voix manager create a record in astdb
(es. for ext 100: DND/100=YES) when dnd is activated, then delete it when DND is deactivated.
The  astdb default family is "DND"
This feature only work if is defined in the asterisk dialplan (extension.conf) and have priority on the local DND behavior.

In this example we send a busy tone if DND is ON.

[your context]
exten =>_1.,1,GotoIf(${DB_EXISTS(DND/${EXTEN})}?s-BUSY,1)

exten=> s-BUSY,1,playtones(busy)

include => services

[services]
exten => *78,1,Answer
exten => *78,n,Wait(1)
exten => *78,n,Macro(DND)
exten => *78,n,NoCDR()
exten => *78,n,hangup

[macro-DND]

exten => s,1,GotoIf($["${DB(DND/${CALLERID(num)})}" = ""]?enable-dnd,1)
exten => s,2,GotoIf($[${DB(DND/${CALLERID(num)})}=YES]?disable-dnd,1)

exten => enable-dnd,1,Set(DB(DND/${CALLERID(num)})=YES)
; IMPORTANT emit DND userevent (asterisk 1.4)
exten => enable-dnd,n,UserEvent(|Act: DND|User: ${CALLERID(num)})
; OR for asterisk 1.2
exten => enable-dnd,n,UserEvent(|Act: DND)
exten => enable-dnd,n,playback(do-not-disturb&activated)

exten => disable-dnd,1,dbDel(DND/${CALLERID(num)})
 ; emit DND userevent
exten => disable-dnd,n,UserEvent(|Act: DND|User: ${CALLERID(num)}) ;<<(asterisk 1.4)
exten => disable-dnd,n,UserEvent(|Act: DND)  ;<<(asterisk 1.2)
exten => disable-dnd,n,playback(do-not-disturb&de-activated)