Figure 6-49.--Dial telephone central office section, cutaway.

of 400 lines or less. A 100-amp unit is required for

electromechanical switches. These switches are called

systems of 500 lines or greater.

crossbar switches.

The crossbar switches are able to switch 10 three-

Digital logic and integrated circuit technology is

wire inputs to any of 30 three-wire outputs, or con-

used to interrupt, decode, determine path availability,

versely 30 inputs to 10 outputs by using these switches

and identify and notify a switch to operate. But,

in a series and parallel combination, the 1 to 999 capa-

the actual voice circuit is completed through

bility (in the 500-line system) is achieved.

Figure 6-49.--Dial telephone central office section, cutaway.

6-61