Editing Rotary dial (section)

==Alphanumeric dialing==
{{Main|Telephone exchange names}}
In addition to the ten digits, the faceplate is often printed with letters corresponding to each position. [[File:US-NJ-LAkewood2697-bell-system-telephone-number-rotary-dial-1940.jpg|thumb|Face of a 1939 Western Electric 302 or 202  rotary dial showing the telephone number LA-2697, which includes the first two letters of Lakewood, New Jersey]]
In North America, traditional dials have letter codes displayed with the numbers under the finger holes in the following pattern: 1, 2 ABC, 3 DEF, 4 GHI, 5 JKL, 6 MNO, 7 PRS, 8 TUV, 9 WXY, and 0 (sometimes Z) Operator. Letters were associated with the dial numbers to represent [[telephone exchange names]] in communities that required multiple central offices. For example, "RE7-3456" represented "REgent 7-3456".

In 1917, W. G. Blauvelt of AT&T developed the combination pattern of letters assigned to each digit, which became the standard in North America. Large cities like New York City would ultimately require a seven-digit telephone number. Some tests in the early 1900s indicated that the short-term memory span of many people was insufficient for seven digits, causing dialing errors (the documentation for these tests is lost).{{Citation needed|date=July 2017}}  As large cities had both manual and automatic exchanges for many years, the numbers for manual or automatic exchanges used the same format, which could be either spoken or dialed.<ref name=fagen1975>''A History of Engineering and Science in the Bell System: The Early Years (1875-1925)'' p578 by M. D. Fagen (editor) & Bell Labs technical staff (1975, Bell Telephone Laboratories)</ref>

In the late 1940s, telephones were redesigned with the numbers and letters displayed on a ring outside the finger wheel to provide better visibility.<ref>{{Cite news|url=http://www.slate.com/articles/life/design/2012/05/telephone_design_a_brief_history_photos_.html |title=Hello?|last=Vanderbilt|first=Tom|date=2012-05-15|newspaper=Slate|language=en-US|issn=1091-2339|access-date=2017-02-04}}</ref>