I have not verified this:
The TTL version of the TXD (transmit data from the Digital Scout to the host computer) signal is available on the Reaction Tune (2.5 mm) jack. However, to gain access to the TTL version of the RXD (receive data from the host computer to the Digital Scout) signal, you would have to open the unit and connect to the TTL side of the HIN202 (RS-232 driver) chip.