Survey of surveys, and the place of the Second Byurakan Survey (SBS) among them is shortly discussed. Deep low-dispersion surveys cover > 10000 sq.degrees, but they managed to study only 15% of this area relatively well.
For 450 SBS objects the slit spectra were obtained on 6 m telescope of SAO. The nature of 120 QS0s,40 Sy galaxies and more than 200 ELG are confirmed. The results of the slit spectroscopy in six SBS fields covering commonly the area of ∼100 sq.degrees are presented.
All surveys, except Byurakan Surveys are extremely poor with Sy galaxies, that is their distinction from other surveys. Weak (16<m<18
5) SBS Sy galaxies sufficiently well filled in the interval between QSOs and Sy galaxies, the efficiency of selection does not much depend on redshifts. There is quite good pass from Sy galaxies to QSOs.