What TV format did Apollo 11 use for its lunar-surface broadcast?

Apollo 11 used slow-scan television for its lunar-surface broadcast. The system transmitted a low-bandwidth black-and-white image from the lunar module’s television camera during the first Moon walk.

Slow-scan television, often abbreviated SSTV, used fewer frames and fewer scanning lines than ordinary broadcast television. That reduced the bandwidth and power needed to send pictures from the Moon, but it also made the raw signal unsuitable for normal television sets on Earth.

At receiving stations, the slow-scan signal was converted into the standard broadcast format used by television networks. This conversion allowed millions of viewers to watch Armstrong and Aldrin, although the resulting image was blurry and ghostly compared with modern video. The original slow-scan recordings later became historically important because the best-quality Apollo 11 television signal was not preserved in full.