Patent ID: 7576804

Claim:
A triax transmitter interface for selectively transmitting video signals having a first or a second field or frame rate on a triax cable, the first field or frame rate being lower than the second field or frame rate, comprising: a video signal input port, a first modulator for modulating a luminance component of a video signal received at said input port onto a first carrier, a second modulator for modulating a chrominance component of the video signal onto a second carrier, and a triax output port for outputting said modulated carriers to a triax cable; wherein said first modulator is a quadrature modulator adapted to modulate luminance components of two video image lines simultaneously and in quadrature onto said first carrier, wherein a first and a second memory are provided upstream of I and Q inputs of the first modulator, respectively, for buffering at least one of the two video image lines to be simultaneously modulated; wherein, when video signals having the first field frame or frame rate are transmitted, the luminance component of each line is applied to a first input of the modulator without being delayed in the memory, a second input of the modulator not receiving a signal, and wherein, when video signals having the second field or frame rate are transmitted each of the first and second memory receives at least one of the two video image lines to be modulated in quadrature, and outputs the respective video image line to the respective first and second input of the first modulator.