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Equipment
Manual Telephone Exchange
In the very early years of the
telephone, a subscriber would lift the earpiece of the telephone
and manually operate a crank on the telephone in order to send a
signal to the switchboard operator. This action would
usually drop a piece of metal on the switchboard associated with
that subscriber's location on the board (called a "drop leaf").
A British friend of mine remembers this being called a "doll's
eye." The operator would plug in an answering cord and
answer. If the called
party was a subscriber on the same switchboard, she would plug
the other cord of the pair in to the called party's location and activate
ringing current in order to ring the called party's telephone.
In later systems of manual telephone
service, the subscriber would lift the receiver of the telephone
and, in doing so, an associated lamp at the switchboard would
light. The operator plugged in and answered.
Depending on whether the called party was a subscriber on the
same board, the operator would complete the call by connecting
and ringing the called party. If the called party was
located in another area, the operator would plug in to an idle
trunk and either dial or keypulse the telephone number or have a
distant operator complete the call.
Automatic Telephone Exchange
Almon Strowger was an undertaker in
Kansas City (some reference Topeka), Kansas. Because his
competitor's wife was a telephone operator and directing all
calls for an undertaker to her husband's business, Strowger was
losing clients. He first conceived his invention in 1888,
and he patented the automatic telephone exchange.
Over the years, several types of
electromechanical telephone systems were used by the Bell
System. Here are some of them:
Step-by-Step
No. 1
No. 350A
No. 355A CDO
(Community Dial Office)
No. 356A
No. 360A
Panel System
Local Panel
Panel Tandem
Crossbar
No. 1 Crossbar
No. 3 Crossbar
No. 4 Crossbar
No. 5 Crossbar
Electronic Switching System (ESS)
No. 1 ESS introduced in Succasunna,
New Jersey, in May 1965.
No. 2 ESS
No. 5 ESS
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