a. A basic x-ray tube filament circuit is seen in figure 3-2. The autotransformer
serves as the power source. In series with the primary of the step-down transformer is
an adjustment called the filament control or choke coil. To set the x-ray tube current,
this adjustment permits variations in the x-ray tube filament temperature. The step-
down, isolation-type transformer shown in figure 3-2 has the filament of the x-ray tube
connected directly across its secondary winding.
Figure 3-2. The mA or filament circuit.