Blending circuit for letters into SECAM colour TV signal - uses blanking of colour signal in region of letters with peripheral residue

摘要

The blending circuit is intended for letters into SECAM colour television signals. It blanks out the SECAM colour signal in the region of the letter to be blended such that the SECAM colour carrier remains at the edge of the region. The letter signal is blended into the dark region. The SECAM carrier may also be allowed to remain over the whole of the area surrounding the letter region. The circuit comprises a frequency-dependent voltage divider (3-7), an electronic switch (8) for the divider connection into the path of the SECAM signal during blanking, and an adder (10) for the divider output ot the letter signal.