TM 5-6675-316-14
(13) The trigger circuit (F) contains a capacitor, an SCR, and a trigger
transformer. When the trigger pulse comes in, and fires the SCR, the capacitor
discharges through the primary of a winding inside the trigger pack (G) firing the
xenon tube. Each selected type size requires a different flash intensity to ensure
correct exposure density. Larger type requires higher intensity and vice-versa.
The microprocessor program determines the flash value for each type size, and a
digital-to-analog converter converts this information into a current.
(14) The flash intensity current is fed to the regulator circuit where it
controls the output level of the dc high voltage supply to the xenon flash tube.
(15) As previously explained, each font disc contains four rows of type, each
in different styles. To access all four rows of type it is necessary to move the
whole font disc laterally so that an adjacent character image track will be
positioned in the exposure window of the light source.
(16) The font disc is moved laterally by a stepping motor which is controlled
by the microprocessor. In this case, the flash cone window is opposite row 1 of the
type. To access rows 2, 3 and 4, the font disc would be moved to the right.
2-16
