http://www.2n.cz/en/products/intercom-systems/ip-intercoms/helios-ip-verso/downloads/#product-content

      1. 2N® IP Vario - press middle quick dial button on the right side
      2. 2N® IP Force, Safety or Uni - press always the first button on the unit.
      3. 2N® IP Verso - press the quick dial button on the basic unit (module)