Figure 7-10.--Block diagram of a preamplifier.

their associated power amplifier to full output. Figure

the microphone and oscillator amplifier of the

7-10 is a block diagram of a preamplifier.

channel selected for use on circuit 1MC. The output

from the power rack is distributed to all circuit 1MC

Power Supply Modules

loudspeaker groups. Alarm signals are not transmitted

over the circuit 6MC loudspeakers. The alarm modules

Two power supply modules are located in the

in the order of their priorty are (1) collision, (2)

control rack. Each power supply is a regulated transistor

chemical, (3) general, (4) unassigned A, and (5) flight

unit that supplies -10 volt dc and -30 volt dc operating

crash.

voltages to the alarm modules and preamplifier

modules.

The order of priority is controlled automatically by

relays in the control rack. Any alarm takes priority over

Alarm Modules

voice announcements.

COLLISION ALARM.-- The collision alarm is a

Ten alarm modules are located in the control

transistorized oscillator circuit that generates a

rack, five for each oscillator group. Each alarm

signal composed of three 1000-Hz bursts. Each

module, when actuated by an alarm contact maker,

burst is 60 milliseconds duration. The first and

is capable of generating an audio-frequency alarm.

second burst is followed by an off time of 60

When an alarm signal is actuated, all microphone

control stations are automatically disconnected by

milliseconds. The third burst is followed by an off

priority relays. The audio-frequency oscillator ouput

time of 420 milliseconds. This cycle repeatedly

(alarm signal) is then connected to the alarm input of

continues as long as power is applied to the circuit.

Figure 7-10.--Block diagram of a preamplifier.

7-11