Differentiating telephone services drove telephone service growth in Chicago at the beginning of the twentieth century. From 1901 to 1906, the total number of telephones in service grew the equivalent of 23% per year.[1] Within that total, private branch exchange telephones and nickel-in-slot 10-party-line payphones grew 33% and 47% per year respectively. Private branch exchanges catered to the needs of large organizations, while nickel-in-slot payphones offered cheap, per-call prepaid service.[2] By August, 1906, these two services accounted for 54% of telephones in use in Chicago.
Plain-old telephone service (POTS) is a term from a later, less dynamic telephone industry.
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Data: Telephones in use in Chicago, 1901-1906, by telephone type (Excel version)
Notes:
[1] These data are from a special telephone report delivered to the Chicago City Council in 1907. The report includes extensive economic and operational data on early nineteenth-century telephone service in Chicago.
[2] Here’s information on long-term trends in business telephone service, and recent developments in private-branch exchange service. On nickel-in-slot telephone service in early nineteenth century Chicago, see John, Richard R. (2010) Network nation: inventing American telecommunications (Cambridge, Mass: Belknap Press of Harvard University Press) pp. 295-8.