(color online) The recorded EIT spectrum of Rb atom in cell 2 by tuning the magnetic field on cell 1. The tuning of the magnetic field on cell 1 can shift the locking point of atoms in cell 1, subsequently driving the probe laser frequency, which scans across the transition resonant lines of atoms in cell 2. The magnetic field on cell 1 varies from 10 G to 25 G while an additional magnetic field of 22.5 G is applied to raise the resonant energy to an appropriate position accessible by the probe laser. The blue and red lines stand for the experimental recordings on two different days, respectively.