Panel switch
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The Panel Machine Switching System is a type of automatic telephone exchange for urban service that was used in the Bell System in the United States for seven decades. The first semi-mechanical types
Panel switch district selector frame at the Connections Museum in Seattle
1948 Western Electric Model 302 telephone set that was installed near Newark airport, and connected to a line of the Newark exchange "BIgelow", the last existing Panel office when it was dismantled in 1983.
Panel ground-cut-off (GCO) line finder brushes
Closeup of all-relay type sender
Strowger switch
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The Strowger switch is the first commercially successful electromechanical stepping switch telephone exchange system. It was developed by the Strowger Automatic Telephone Exchange Company founded in 1
Panel switch
…and Office Group parameters. Panel Sender Tandems were also used when their greater capabilities were worth their additional cost. While the Strowger (step-by-step) switch moved under direct control of dial pulses that came from the telephone dial, the more sophisticated Panel switch had senders, which registered…
Western Electric 7A Rotary, friction drive (Bird-cage), No. 7001 Line Finder. Note the driven bevel gear on the right-hand side; this type has a steady rotary motion and does not employ an electromagnet for stepping.
Bank of two-motion switches
British SXS two-motion contact bank
Télégraphie, Systeme Strowger