Editing Slow-scan television (section)

===Scanlines===
[[File:Moderni SSTV.jpg|thumb|left|Slow-scan test card]]
A transmission consists of horizontal [[line (video)|lines]], scanned from left to right. The color components are sent separately one line after another. The color encoding and order of transmission can vary between modes. Most modes use an [[RGB color model]]; some modes are black-and-white, with only one channel being sent; other modes use a YC color model, which consists of [[luminance]] (Y) and [[chrominance]] (R–Y and B–Y). The modulating frequency changes between 1,500 and 2,300&nbsp;Hz, corresponding to the intensity ([[brightness]]) of the color component. The modulation is analog, so even though the horizontal resolution is often defined as 256 or 320 pixels, they can be sampled using any rate. The image [[aspect ratio (image)|aspect ratio]] is conventionally 4:3. Lines usually end in a 1,200&nbsp;Hz horizontal synchronization pulse of 5&nbsp;milliseconds (after all color components of the line have been sent); in some modes, the synchronization pulse lies in the middle of the line.