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As telephone systems grew, switchboards grew larger. However, one
operator could not reach enough connections to do all the work at
one position and boards were linked in a series with an operator at
The first automatic switching systems worked best with small
networks. Edmonton had the first automatic system in Alberta,
installed in 1908. Larger centres like New York and Toronto
continued with manual systems until 1922. (The last of the manual
equipment in New York was replaced by dial units in 1960.)
Early automatic systems were known as Step by Step because they
made the connection in a series of steps as the number was dialed.
The rotary dial sent electrical pulses which activated
electromagnets in the switching unit. The electromagnets moved
components into position to create the desired connection to the
number you were calling.
This brief video contains examples of telephone automatic switching
technology. There are 3 main types of switching technology: Step by
Step, X Bar, and Digital Electronic. The Step by Step switching
technology is featured here.
The system components could get stuck so regular maintenance by
switchmen was important. Apprentice switchmen learned on the job
over a period of five or six years before they became journeymen. On
Sundays, they were often on their own in the exchange building or
wire centre. This offered a good learning experience if things were
quiet but it was a real challenge if a storm created short circuits
and the system began to overload.
When the Edmonton system was converted from three-wire to
two-wire, service improved and complaints dropped from an average of
fifteen complaints per telephone per year to two complaints per
telephone per year.
The Step by Step equipment was bulky and needed large exchange
buildings or wire centres. The equipment was also very noisy. As
demand for telephone service continued to grow, more efficient and
compact switching equipment was developed. The next advance was
Crossbar. It was still an electro-mechanical system using
electromagnets. However, it did not complete the circuit until all
the digits in the phone number were dialed. This feature gave it
more flexibility in routing calls. It could place more calls with
fewer components. The first units in Alberta were installed in
Calgary in 1958.
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Heritage Community Foundation and
Telephone Historical Centre All Rights Reserved