voltage compensators (devices number four and number five). The line-voltage
compensator meter (device number three) indicates the number of volts per turn on the
autotransformer. Now the voltage is impressed over all the turns of the autotransformer
(device number six). From here, it is channeled into three different circuits.
b. The first of the three is the primary circuit. The kV selectors (devices number
seven and number eight) select the voltage to be impressed on the primary circuit and,
in turn, the high-voltage circuit. After the kV has been selected, the kV meter
(prereading voltmeter) (device number nine) indicates what the resulting kV will be. The
timer circuit (device number ten) is also located in the primary circuit along with the
circuit breaker (device number 11). The voltage is then fed into the primary of the step-
up transformer (device number 12).
c. There are taps (points a and b) that connect the rectifier transformers with the
autotransformer. The lines from the autotransformer lead to the valve-tube (step-down)
transformers (device number 15). These transformers supply the increased amperage
needed by the tubes within the vacuum-tube rectification circuit (device number 14).
d. Taps c and d channel the voltage, taken off a certain number of turns of the
autotransformer, to the filament transformer (device number 17), which is used to
supply milliamperage in the filament circuit. This circuit is controlled by one of three
arrangements: a tap-selector resistor (device number 18A), an adjustable resistor
(device number 18B), or a choke coil (device number 18C). There is sometimes a
filament ammeter in this circuit, although it is not shown in figure 3-5.
e. On the secondary side of the high-voltage transformer (device number 12),
we find the high-voltage circuit. Within this circuit, we find the mA meter (device number
13), the bridge-type rectifier (device number 14), and the x-ray tube itself (device
number 16). All these are activated when the step-up transformer is activated, and the
exposure is actually being made.