help with voltage comparator

pls,help me with a circuit that can compare three 3 different voltages.each occuring when there is a voltage drop to a certing level.let say voltage A when a certain voltage drop occurs.the same applies to B AND C.none will switch with the other.this is found in our automatic voltagt regulators

Sorry.... Don't get your idea....

You want to switch between regulated output voltages ? and want the switch to be triggered by certain input voltages ?

Or is it something else ?

comparator

hi ,thanks for ur respond.yes i want to regulate from an unregulated voltage. if my 220ac voltage drops,the comparetor will swiitch to a lower dc voltege,hence the,ralay activated while the other two remain open.please help me