a subcarrier phase locked loop not shown in a conventional manner and represents the phase of the v signal in the composite video signal this signal normally alternates every second line between 1 and 1 if pal switch corresponds to a 1 the output of multiplier 52 is equal to the output of multiplexer 50 whereas if the pal switch corresponds to a 1 the output of the multiplier 52 is equal to the negative value of the output of multiplexer 50 the output of summer 46 is the sum of the previous sample from line memory 42 and the second previous line sample from line memory 49 the output of summer 54 is the sum of the output of summer 45 and multiplier 52 the output of divider 56 is the output of sum 3 divided by 2 corresponding to the values given in table 1 for each value of phase in pal switch table 1______________________________________ phase 0 phase 1______________________________________pal sub sw 1 1 2 u 39 sub i 1 2 v 39 sub i v 39 sub i 1 1 2 v 39 sub i 1 2 u 39 sub i u 39 sub i 1 pal sub sw 1 1 2 u 39 sub i 1 2 v 39 sub i v 39 sub i 1 1 2 v 39 sub i 1 2 u 39 sub i u 39 sub i 1 ______________________________________ where each of the u 39 i v 39 i u 39 i 1 and v 39 i 1 are in the n 1 pixel and are thus u 39 i n 1 v 39 i n 1 u 39 i 1 n 1 and v 39 i 2 n 1 in the pal implementation a 13 5 mhz clock signal.