Had the modern trend for square pixels applied, this would have yielded a 2048x1152 sampling grid. There was no such requirement in the standard, though, since CRT monitors don't need any extra scaling to be able to show non-square pixels. According to the specification, the sampling rate for the interlaced input to use was 72 MHz, resulting in 72 x 26.67 = 1920 horizontal samples. It was then reconverted to 1440 from within the sampled domain. The input signal often originated from sources previously sampled at only 54 MHz, for economical reasons, and therefore already containing no more than the analogue equivalent of 1440 samples per line.