output signals designated 34 d 34 of subtractor u11 on terminals s thereof are provided as input signals to adder u12 on the terminals b0 b1 b5 thereof the a terminals a0 al a8 of latch u12 are hard wired to the blanking voltage level vcc and to ground thus the input signals on terminals b0 b1 b5 of adder u12 are one eighth of the transition quantity d i e the difference due to the elimination of the three least significant bits shift left three times by subtractor u11 from the video difference value thus adder u12 is adding one eighth of the video transition quantity d to the hardwired blanking input value and providing the sum blanking 1 8 u00b7 d at the output terminals s 7 0 of adder u12 this is only an eight bit number since bit 8 will be always 0 by definition of the video signal where the largest value is 168 the output terminals s 7 0 of subtractor u11 are also connected to the b input terminals of the second adder u16 at terminals b0 b1 b7 of adder u16 as can be seen adder u16 is an eight bit adder adder u12 is a seven.