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| | The Early Years of the Strowger System by R.B. Hill |
 | | Strowger is said to have constructed the first crude model of his switch from a cardboard collar box and a paper of pins. |
 | | Strowger filed his patent application on March 12, 1889, and it was issued on March 10,1891 as patent No. 447,918. |
 | | Early in 1908, the first Strowger straight two-wire system, in which the ground was eliminated, was installed at Pontiac, Ill. This was accomplished by the use of a sluggish, or slow-release, relay which, when energized by a current, held its contacts closed for a short period after the circuit through its winding had been broken. |
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