ISDNCid is a CAPI-based ISDN (Common ISDN API) application with caller ID, answering machine, fax reception, and external program launching capabilities. This program serves as an answering machine, fax receptor, caller id displayer, and can launch external programs as well. Unwanted callers can be blocked, and it runs as a convenient icon in the System Tray area of the Windows taskbar, popping out with every incoming message, call, or fax (if configured to do so). The answering machine may be set up with answering delay and maximum message time, and received faxes are saved in TIFF format.Additionally, external programs or batch files can be launched with run parameters on incoming calls or when the call is cleared.