STI-II – Smart Telephone Interface (Special Order) Available by special order. The STI-II provides a self-nulling hybrid interface between a single POTS line and a users PC COM port. The STI-II is equipped with a programmable serial port, allowing control and monitoring via the users PC application software. This product makes those remote call-in recording a snap while eliminating the DTMF tones. Various LEDs, relays, pushbuttons, dip-switches and RS-232 serial port comprises the user interface to the STI-II. Two modes of operation are supported: program and command.