Where did 625 line television come from?

[Richard_FM]

Should have said a bit more in previous post. 605 and 625 are so close that there's no real difference between them. 625 causes less trouble with early dividers. So why even bother with 605.

819 = 3 * 3 * 7 *13 but by then dividers were a bit easier. Doing divide by 13 the old fashioned way with locked blocking oscillators would have been very hairy.

I did wonder how the French ended up with such an odd amount of lines.  Some early experiments were for over 1000 lines.