<P> In addition to the numbers, the faceplate is often printed with letters corresponding to each finger hole . 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 having more than 9,999 telephone lines, and additionally given a meaningful mnemonic to facilitate memorization of individual telephone numbers by incorporating their exchange names . For example: "RE7 - xxxx" represented "REgent 7 - xxxx",' Regent' being a local exchange name used in Canada, derived from an earlier precursor telephone number,' 7xxxx'--with callers actually dialing' 73 - 7xxxx' (737 - xxxx). </P> <P> The use of letters on dials was proposed in 1917 by W.G. Blauvelt of AT&T . Large cities like New York would ultimately require a seven - digit number, but some tests in the early 1900s indicated that the short - term memory span of many people could not handle seven digits and many dialling errors due to memory lapse might occur (the documentation for these tests is lost). Hence the first Panel automatic exchanges cutover in 1915 in Newark, New Jersey used "semiautomatic" operation with the local operator keying the number for the caller . And as large cities would have both manual and automatic exchanges for some years, the numbers for manual or automatic exchanges would have the same format (originally MULberry 3456, with three letters then four numbers), which could be either spoken or dialled . </P> <P> In the United Kingdom the letter "O" was combined with the digit "0" rather than "6". Older Australian rotary dial telephones also had letters, but the combinations were often printed in the center plate adjacent to the number . The Australian letter - to - number mapping was A = 1, B = 2, F = 3, J = 4, L = 5, M = 6, U = 7, W = 8, X = 9, Y = 0, so the phone number BX 3701 was in fact 29 3701 . When Australia changed to all - numeric telephone numbers, a mnemonic to help people associate letters with numbers was the sentence, "All Big Fish Jump Like Mad Under Water eXcept Yabbies ." However, such letter codes were not used in all countries . </P> <P> Dials outside Canada, the United States, and large cities in Britain (before all - figure dialling) usually did not bear alphabetic characters or an indication of the word "operator" in addition to numbers . Alphabetic designation of exchanges with Cyrillic letters (А, Б, В, Г, Д, Е, Ж, И, К, Л for each of the digits from 1 through 0 respectively) was also used for a short period in the Soviet Union in the 1950s and 1960s, but by the next decade this practice was largely discontinued . </P>

When did they stop making rotary dial phones