Binary stars

What are the types of binary stars? How is mass measured in each type of binary? The types of binary stars are as follows: Visual binary is a star system whose members are bright and widely separated. The component stars of this system can be individually resolved through telescope from the earth. This system is relatively close to us. Mass in this system can be calculated by determining the distance, Semi major axis and the binary period. Spectroscopic Binary is a star system, which is very distant from us. The stars in this system seem too close to each other, which makes their study harder. Although the stars in this system cannot be directly resolved, the back and forth Doppler shifts of their spectral lines are monitored to perceive them. The mass in this system is very hard to find because of the insufficient information, but the velocity can be calculated. Eclipsing Binary is very rare. The stars in this system are aligned in such a way that from earth we see one star passing in front of the other or eclipsing. Only the ratio of the component masses can determined with the stars in this system.