Figure 7-8.--Simplified block diagram of 1MC-6MC central amplifier announcing system.
The control rack (fig. 7-9) is a
bulkh ead-mou n ted enc losu r e c on tain in g the
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.
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
microphone and alarm signals to drive
Figure 7-9.--Control rack.