There are four arrangements of the central office
The central office switchboard houses the
system (200, 300, 400, 500 line). The system is
components that interconnect the calling telephone
expandable to a 700-line capacity; however, the
with the called telephone. The switching and control
manufacturer should be consulted should this need
circuit components are the crossbar switches and
arise. The various configurations (line capacity)
circuit cards mounted in the card cage in a cabinet.
operate in the same way. The difference between the
Two dc-to-dc converter power supplies supply logic
arrangements is the capability to interconnect more
voltages for these circuits. The number of lines that
lines through more paths and links. Switching
can be connected within a system depends on the
c a p a c i t y (trunking) established by military
number of cabinets.
specification is 16 percent of line capacity.
The central office switchboard's (fig. 6-49)
There are four areas not duplicated as the system
primary job is to (1) interpret the dial pulse
expands. These are the power supply, ring generators,
information from the calling telephone, (2) determine
emergency cut-in, and manual switchboard. The
the called telephone, (3) choose a suitable path to
power supply and ring generators are able to serve any
interconnect the two telephones, and (4) connect the
arrangement. The emergency cut-in and manual
two telephones and ring the called party. Its secondary
switchboard are only required once. Although one
task is to notify a station, in an off-hook condition, to
power supply is required for any system
configuration, a 50-amp unit is required for systems
hang up the handset.
Figure 6-48.--Dial telephone central office.