5UP7

"5UP7" is a cathode ray tube developed in the 1940s for use in oscilloscopes and spectrum analyzers.

My first views of slow scan television (SSTV) images came through a 5UP7 CRT in 1980.  The 5UP7 along with some homebuilt electronics and an old oscilloscope permitted reception of SSTV images on the HF amateur bands from all corners of the world.