# Configure External Applications

External applications allow servers to use serial or IP ports to control an external device by sending signals over data links. The data links can be direct serial connections to the PBX, they can connect to modems that are connected to analog ports on the PBX (the modem is used to "forward" DTMF signals to the PBX), or they can be direct IP connections.

External applications are programmed using the External Applications menu of the Web Console. Click the following links for application-specific instructions:

- Message Waiting Indicator Applications (including RS-232 MWI)

- Property Management Services (PMS)

- SMS Notification (UK Only)

- Other External Applications (parameters reference)