The following extensions should be inserted in the main phone number +420 326 551 111, substituting the last two digits. When calling the extension 11 (or the GSM gate) only, the exchange will ask you to select another extension (DISA extension). If no extension is selected, the exchange first rings the operator (extension 11), and if there is no answer the call is forwarded to all telephones in the business department. Calling any other number, the call is only passed on to the recipient's phone.