Overview

The Intercom feature provides the ability to establish auto-answered calls on snom IP phones allowing paging among them. A typical use case would be an announcement in an office environment you would like to make from one colleague to another or to a group of colleagues, respectively. It is only usable with Snom Desk IP Phones "D Series". Restrictions may apply in certain SIP Server environments.

Configuration

• Calling phone

  1. Via web user interface configure any free Function Key as type Intercom.
  2. Type in the extension (can be single or call group) you want to announce the call to

• Called phone(s)

  1. Via web user interface configure the setting: Advanced → Behavior : Intercom Policy to "Always"
  2. Via Auto Provisisoning use setting answer_after_policy accordingly.
  3. If there already is an active call, even if answer_after_policy is set to "always", remember that call_waiting needs to be enabled

Usage

• Calling phone

  1. Press the configured intercom function key

     • The phone calls the configured extension

  2. Hang up the receiver.

     • Intercom call will be closed as any normal call.

• Called phone(s)

  1. Incoming Intercom calls will be auto-answered, i.e. no there is no ringtone announcing the call. The microphone is immediately activated!
  2. The call can be closed at anytime by hanging up or pressing the Cancel key.

Technical Background

• Calling phone

  • An SIP INVITE message containing the "Alert-Info" Header will be sent out. The "Alert-Info" Header will force the called extension(s) to auto-answer the call.

Alert-Info: <http://www.notused.com>;info=alert-autoanswer;delay=0

• SIP PBX

  • SIP PBX may alter the Alert-Info Header, for being a safety-relevant feature. Therefore the described functionality can only be achieved when the SIP INVITE is received unaltered.