selected as the information-sending device to the
alerting watch standers of existing troubles within the
many gyrocompass repeaters of the system. In
systems. The components commonly used with main
addition, each of the individual repeaters in the system
IC switchboards are ABT devices, switches, bus
may be cut in or out of the system without having any
failure alarm units, fuses and fuse holders, lamps and
adverse effect on the operation of the system. The
switches for the other systems may be used in the same
indicators, and power monitoring instruments,
manner as those for the gyrocompass.
ABT DEVICE.-- The ABT device used with IC
A bank of SR switches is also located on the ACO
switchboards transfers the load from the preferred
section of some switchboards. These switches are used
source of supply if it fails to an alternate source that
to isolate the various speaker groups and alarm contact
remains energized. When the preferred source is
makers of the general announcing system circuit 1MC.
restored, the load is then transferred back to the
preferred source automatically by the ABT device.
ABTs are designed for use in ac or dc, and 60- or
ABTs may have either two or three bus transfer
There are several components used with the main
switch positions. Bus transfer switch positions indicate
IC switchboards. The need for these components
the number of power supplies the ABT is designed to
range from providing a means of receiving and
handle. Two-way transfers indicate that the ABT is
distributing power to the various IC systems to
Figure 3-6.--Pictora1 view of ABT-1A2.