Figure 6-48.--Dial telephone central office.

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.

6-60