Direct Inward System Access

Direct Inward System Access ( DISA ) is a function within telecommunication systems that enables a telephone system to be accessed from outside in such a way that the calling connection appears as part of the telecommunication structure called. So z. B. a home office (outside of your own company) to a called third party appear to be internal to the company or to and from an employee's mobile phone with a company number (for example to save telephone costs by means of call-through ).

The DISA function must be implemented carefully, as it can otherwise be misused by unauthorized persons as a backdoor , for example to provide premium value-added services (0900 numbers) such as telephone numbers at the expense of the telephone system owner . B. Use adult entertainment.