PURPOSE: To prevent color information from being lost by modulating color burst signals in position by additional information in the system where additional information is superposed onto television signals.

CONSTITUTION: Time width Td of gate signal G is increased or reduced according to contents of additional information by integral multiples of one period T of color burst signals. Gate signal G2 rises simultaneously with the rise of gate signal G1 and has a time width which covers completely the eight-cycle color burst signal. The position of gate signal G2 is modulated by time width Td of gate signal G1 which synchronizes with the horizontal synchronizing signal, and eight-cycle components of the reference burst signal are taken out by gate signal G2 and are superposed as color burst onto video signals.