Early Color Television
Col-R-Tel Model 100-1 Converter
(click on picture for high resolution image)
The Col-R-Tel was designed to be put in front of a ten inch black and white TV set to convert it to NTSC color. It has a large plastic wheel with segments containing each of the three primary colors. The wheel is turned by a small electric motor. A chassis is mounted on the rear of the TV set, and connections are made to various places inside the set. The Col-R-Tel was first sold about1955. The Col-R-Tel sold for about $150, far less than a color receiver.
Col-R-Tel worked by extracting the red, blue and green video information from the NTSC signal and sequentially applying the signal to the picture tube in the black and white set, so that the red signal was applied when the red filter was in front of the screen, the blue signal when the blue was in front, and the green signal when the green filter was in front. The vertical syncronizing pulse was used to control the speed of the motor to keep the proper filter in place at the proper time.
These converters produce a reasonably good color picture, but would only work with very small screen sets.