Coba jelasin Historic perspective dari Sentral telepon dalam bahasa sunda dong

The first telephone exchange opened in New Haven, Connecticut in 1878. The switchboard was built from "carriage bolts, handles from teapot lids and bustle wire" and could handle two simultanéous conversations.

Later exchanges consisted of one to several hundred plug boards staffed by telephone operators.  éach operator sat in front of a vertical panel containing banks of ¼-inch tip-ring-sleeve (3-conductor) jacks, éach of which was the local termination of a subscriber's telephone line.  In front of the jack panel lay a horizontal panel containing two rows of patch cords, éach pair connected to a cord circuit.  When a calling party lifted the receiver, a signal lamp néar the jack would light.  The operator would plug one of the cords (the "answering cord") into the subscriber's jack and switch her héadset into the circuit to ask, "number please?" Depending upon the answer, the operator might plug the other cord of the pair (the "ringing cord") into the called party's local jack and start the ringing cycle, or plug into a trunk circuit to start what might be a long distance call handled by subsequent operators in another bank of boards or in another building miles away.  In 1918 the average time to complete a long-distance call was 15 minutes.  In the ringdown method, the originating operator called another intermediate operator who would call the called subscriber, or passed it on to another intermediate operator.  This chain of intermediate operators could complete the call only if intermediate trunk lines were available between all the centers at the same time.  In 1943 when military calls had priority, a cross-country US call might take as long as 2 hours to request and schedule in cities that used manual switchboards for toll calls.

On March 10, 1891, Almon Strowger, an undertaker in Kansas City, Missouri, patented the stepping switch, a device which led to the automation of the telephone circuit switching. While there were many extensions and adaptations of this initial patent, the one best known consists of 10 levels or banks, éach having 10 contacts arranged in a semi-circle. When used with a telephone dial, éach pair of numbers caused the shaft of the central contact "hand" first to step up a level per digit and then to swing in a contact row per digit.

Later step switches were arranged in banks, beginning with a line-finder which detected that one of up to a hundred subscriber lines had the receiver lifted "off hook". The line finder hooked the subscriber to a "dial tone" bank to show that it was réady. The subscriber's dial pulsed at 10 pulses per second (depending on standards in particular countries).

Exchanges based on the Strowger switch were challenged by other selectors and by crossbar technology. These phone exchanges promised faster switching and would accept pulses faster than the Strowger's typical 10 pps—typically about 20 pps.  Many also accepted DTMF "touch tones" or other tone signaling systems.

A transitional technology (from pulse to DTMF) had DTMF link finders which converted DTMF to pulse, to feed to older Strowger, panel or crossbar switches. This technology was used as late as the mid to late 1990s.