  The rigorous dark-sate conditions, i.e., two-photon resonance, for a
Lambda-type electromagnetically induced transparency (EIT) are extended with
the system controlled by a microwave field. The extended dark-states are found
to be extremely sensitive to the phase of the microwave field in a narrow
interval. However, the dark-state is no longer the requirement for EIT in this
scheme and EIT without dark states is present.
