Figure 5-7.-New optical sight with CRT.
the information. Figure 5-7 shows an example of a
modern electro-optical sight. This unit or system is
known as a heads-up display (HUD).
The HUD receives computed attack and
navigational input signals from a tactical computer,
aircraft performance data from aircraft flight sensors,
and discrete signals from various aircraft systems
(fig. 5-8). Information received from these sources is
displayed on a transparent mirror (combiner) located
directly in front of the pilot at eye level. The HUD
processes these signals in the signal data processor.
These signals are then applied to the display unit as X
(horizontal), Y (vertical), and Z (bright-up) signals
that provide the symbols that appear on the combiner.
The symbols are focused to infinity and are
superimposed over real world objects in line with the
aircraft flight path. Certain symbols are positioned on
the combiner to correspond with real world object
positions relative to the aircraft, even though the real
world object may not be visible.
This section will discuss the two major com-
ponents of a HUD setthe signal data processor and
the heads-up display unit.
Signal Data Processor
Three-phase ac power is applied to six different
rectifiers contained in the low-voltage power supply.
The ac voltage is rectified by each rectifier, and then
regulated to a precise value. Each value of dc supply
voltage is distributed for circuit operation through the
signal data processor.
INPUT RECEIVERS. Digital data signals are
applied to the input receivers on four channels. Data
transfer is in serial form, and all four channels are in
operation at the same time. Each channel consists of
a signal and a signal-return line. Specific input data is
applied to each channel as follows:
1. Channel one receives a data word signal and a
data word signal return.
2. Channel two receives the data identity signal
and a data identity signal return.
3. Channel three receives a data ready signal and
a data ready return signal.
4. Channel four receives a data clock signal and
a data clock return signal.
Data identity signals are transmitted simul-
taneously with each data word signal. They identify
the data word. The identity signal consists of 20 bits
of data, which include the control bit, data identity,
and parity bit.