All picture tubes, whether monochrome or color type are identified by a specific code consisting of numbers and letters. The codes are different from each other because different tubes have different characteristics.

For example, a certain monitor colour picture tube may have the designation, M34AFA63X03 that can breakdown into 6 parts: M/34/AFA/63/X/03

Part 1: Application

Computer monitor tubes start with the letter "M” while for a TV picture tube, it start with “A”.

Part 2: Screen diagonal measure in centimeters (cm)

The “34” means the diagonal viewing measure is a minimum of 34cm which refers to 14” tube, 36cm is 15”, 41cm is 17” and so on.

Part 3: Family code

The three letters “AFA” designate a family of tubes that have similar physical and electrical characteristic. These letters are assigned alphabetically beginning with “AAA”, followed by “AAB”, “AAC” etc.

Part 4: Family number

The number 63 shows a specific tube within the family code. A different number is assigned to tubes within the same family that have different neck diameters, for example a single digit would be a monochrome tube, but this two-digit number shows it is colour.

Part 5: Phosphor Type The fifth symbol gives the phosphor designation. The letter X here corresponds to P22 for colour picture tubes. Colour monitor tubes can have any other single letter (excluding I, O, or W) to designate other phosphor type for various applications. For monochrome pictures, the phosphor symbol is WW, corresponding to P4. Monochrome monitor tubes also can use WW or some other two-letter combination (excluding I and O).

Part 6: Integral neck components The sixth symbol is assigned only for tubes having integral neck components, such as the deflection yoke. The specs are only apply to a particular tube manufacturer. The primary consideration here is winding inductance. The yoke coils have different sensitivity i.e. deflection per Amp in both horizontal and vertical.