819 line

819-line was an analog monochrome TV system developed and used in France[1][2] as television broadcast resumed after World War II.

[8][9] The system was also adopted (with limited bandwidth, affecting image resolution) in 1953 in Belgium[1][4] by RTB and in 1955 in Luxembourg by Télé-Luxembourg.

[13][14] However, the theoretical picture quality far exceeded the capabilities of the analogue equipment of its time, and each 819-line channel occupied a wide 14 MHz of VHF bandwidth.

Thus even an unusually crisp "standard" definition (or slightly soft 405-line) image only needed half, or even one-quarter the vision bandwidth of the 819-line system to give a "balanced" appearance, despite their lower overall resolution still seeming perfectly clear on the more affordable small-screen receivers often used in the pre-color era.

With the usual additions of sound carrier and vestigial sideband the result was a combined signal that demanded approximately two to three times the bandwidth of more moderately specified standards, even when colour was added to them (as the color subcarrier resides within the luma signal space).