Audio Monitoring - Listen In

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This article describes how to monitor the audio from selected stations using Simplex Conference in an ICX-AlphaCom or AlphaCom XE system. The microphone on the monitored station will be activated without any connection or ringing tone. Optionally also the call LED can be deactivated.

There is one or more Staff stations and a number of stations that can be monitored. The Staff station can select which station to monitor by pressing a DAK key and then dialing the station directory number, alternatively selecting a preconfigured DAK key.


  • Start monitoring: Dial 9535 + station number (these numbers can be configured on preconfigured DAK keys).
  • Stop monitoring: Dial 9535 + 9535 (or press dedicated DAK key twice).

If a new station is selected for monitoring, the currently monitored station will not be monitored anymore.

The Staff station can monitor one station at a time.

For monitoring multiple stations simultaneously, please see Multiconference.


Include the Staff station(s) in UDP Group 1, and assign it to a simplex conference in the User Defined Parameter (EXP) field:

  • Staff station 1 assigned to Simplex Conference 8201
  • Staff station 2 assigned to Simplex Conference 8202
  • Etc...
Setting UDP 1 and defining %exp

The Staff station must be set as a default member in the Simplex Conference it is assigned to:

Defining Simplex Conference default member

DAK1 on the Staff station is programmed with the default Two Step Event Trigger w/User Parameter, 9535 (feature 95/0). The programmed event reads the dialed directory number and commands the substation to enter a conference as speaker. To turn off the monitoring, press DAK1 again.

Event Handler programming

An Event trigger start event is used to clear the previous monitored station:

Clear the previous monitored station

Action commands:

$CONF L%udd(%1.phy) L8200
IND %1.phy %1.dak(I%udd(%1.phy)) 2 2 OFF

The main event:

Monitoring main event

Action commands:

$DISCON_ST L%1.dir
IF %op(%2.dir,=,9535)
$CONF L%udd(%1.phy) L8200
WUDD %1.phy %2.dir
$CONF L%2.dir L%1.exp U2
$CONF_TALK L%2.dir U2 U1
IND %1.phy %1.dak(I%2.dir) 2 2 ON
$DTS L%1.dir 'Monitoring' U1
$DTS L%1.dir '%2.nam' U2
$DIP L%2.dir "ind stl 0 0"             {Turn microphone LED off for INCA stations}
$DIP L%2.dir "stinfo 5 'LedOff'"       {Turn microphone LED off for Turbine stations}

OBS icon The last three command lines in the action string are only applicable for IP stations

Note icon If the Call LED should be ON during monitoring, the last three lines in the action string above should be deleted.


Simplex conferences survive a server restart, indications and conference talk control do not. To prevent unintentional audio all Simplex conferences should be switched off at server restart using this event:

Turn Simplex Conference OFF to all stations in group 84 (which by default is all stations)

Action commands:

$CONF L84 L8200