Figure 7-9.--Control rack.

Figure 7-8.--Simplified block diagram of 1MC-6MC central amplifier announcing system.

CONTROL RACK

The control rack (fig. 7-9) is a

bulkh ead-mou n ted enc losu r e c on tain in g the

pr eamplifier modules, power supply modules,

osc illator alar m modules, and the sy stem

switc h ing and tr ansfer r in g c on tr ols and

indic ator s. The r ac k also c on tain s the c on tr ol

and power r elay s, the r elay power supply , and

the terminal boards for making connections to

the ship' s w ir in g .

The control rack preamplifier voice and

alarm signals from the microphone control

stations, routes them to the power rack for

amplification, and then transmits them to the

various loudspeaker groups.

Preamplifier Modules

Two preamplifier modules are located in

the control rack one for each amplifier channel.

Each preamplifier contains four transistor-

amplifier stages for increasing the low-level

7.176

microphone and alarm signals to drive

Figure 7-9.--Control rack.

7-10