(i) The first stop seems to be in empty space three light years beyond the red giant Antares. However, the target is a widely orbiting green companion star which happens at the time to be directly between the ship and Antares.
Sending the recognition signal by phase-velocity transmission, called "ultraphone" in other Blish works, which travels at about 125% light speed, Langer, Jack and Sandbag receive a reply within a mere two days, demonstrating that a nearby robot station, receiving their transmission, is communicating with the system of the green star by some other, much faster, means. Blish readers know of the instantaneous Dirac transmitter, which works by inter-particle action at a distance, and the instantaneous CirCon radio, which reaches around the continuum to detect radio signals currently transmitted at interstellar distances.
A voice in heavily accented English informs them that they are in a military area and must proceed directly to their next stop. That is their only contact with the first stop although even that enables Langer to deduce something about the attitudes of the entities involved.
OK, summarising the journey in appropriate detail is requiring more time than I had anticipated so this summary will have to be serialised.