Editing Telegraph key (section)

===Double-lever paddles===
Keys having two separate levers, one for ''dits'' and the other for ''dahs'' are called dual or dual-lever paddles. With a dual paddle both contacts may be closed simultaneously, enabling the "[[Iamb (poetry)|iambic]]"{{efn|name=iamb_trochee_note}} functions of an electronic keyer that is designed to support them: By pressing both paddles (squeezing the levers together) the operator can create a series of alternating ''dits'' and ''dahs'', analogous to a sequence of [[iamb (poetry)|iambs in poetry]].<ref>{{cite web |first=Anthony, {{sc|K3NG}} |last=Good |date=22 April 2023 |title=Arduino CW keyer |department=Radio artisan |type=blog |url=http://blog.radioartisan.com/arduino-cw-keyer/ |via=radioartisan.com |access-date=27 October 2024 |archive-date=20 February 2013 |archive-url=https://web.archive.org/web/20130220013955/http://blog.radioartisan.com/arduino-cw-keyer/ |url-status=live }}</ref><ref>{{youTube|ZdzjvIk_aY0|How to use an iambic keyer}}.</ref> For that reason, dual paddles are sometimes called ''squeeze keys'' or ''iambic keys''. Typical dual-paddle keys' levers move horizontally, like the earlier single-paddle keys, as opposed to how the original "straight-keys'" arms move up-and-down.

Whether the sequence begins with a ''dit'' or a ''dah'' is determined by which lever makes contact first: If the ''dah'' lever is closed first, then the first element will be a ''dah'', so the string of elements will be similar to a sequence of [[trochee]]s in poetry, and the method could logically just as well be called ''"trochaic keying"'' ({{morse|dash|dot|dash|dot|dash|dot|dash}}). If the ''dit'' lever makes first contact, then the string begins with a ''dit'' ({{morse|dot|dash|dot|dash|dot|dash|dot}}).

Insofar as iambic{{efn|name=iamb_trochee_note}} keying is a function of the electronic keyer, it is not correct, technically, to refer to a dual paddle key ''itself'' as "iambic", although this is commonly done in marketing. A dual paddle key is required for iambic sending, which also requires an iambic keyer. But any single- or dual-paddle key can be used non-iambicly, without squeezing, and there were electronic keyers made which did not have iambic functions.

Iambic keying or squeeze keying reduces the key strokes or hand movements necessary to make some characters, e.g. the letter&nbsp;C, which can be sent by merely squeezing the two paddles together. With a single-paddle or non-iambic keyer, the hand motion would require alternating four times for {{sc|'''C'''}} (''dah''-''dit''-''dah''-''dit'' {{morse|dash|dot|dash|dot}}).

The efficiency of iambic keying has recently been discussed in terms of movements per character and timings for high speed CW, with the author concluding that the timing difficulties of correctly operating a keyer iambicly at high speed outweigh any small benefits.<ref>{{cite web |title=Iambic keying – debunking the myth |first=Marshall G., {{sc|N1FN}} |last=Emm |url=http://www.morsex.com/pubs/iambicmyth.pdf |via=morsex.com |access-date=2022-11-09 |archive-date=2022-10-25 |archive-url=https://web.archive.org/web/20221025230904/http://morsex.com/pubs/iambicmyth.pdf |url-status=live }}</ref>

Iambic keyers function in one of at least two major modes: Mode&nbsp;{{sc|A}} and mode&nbsp;{{sc|B}}. There is a third, rarely available mode&nbsp;{{sc|U}}.

==== Mode {{sc|A}} ====
Mode&nbsp;{{sc|A}} is the original iambic mode, in which alternate dots and dashes are produced as long as both paddles are depressed. Mode&nbsp;{{sc|A}} is essentially "what you hear is what you get": When the paddles are released, the keying stops with the last dot or dash that was being sent while the paddles were held.

==== Mode {{sc|B}} ====
Mode&nbsp;{{sc|B}} is the second mode, which devolved from a logic error in an early iambic keyer.{{citation needed|date=March 2018}} Over the years iambic mode&nbsp;{{sc|B}} has become something of a standard and is the default setting in most keyers.

In mode&nbsp;{{sc|B}}, dots and dashes are produced as long as both paddles are depressed. When the paddles are released, the keying continues by sending ''one more element'' than has already been heard. I.e., if the paddles were released during a ''dah'' then the last element sent will be a following ''dit''; if the paddles were released during a ''dit'' then the sequence will end with the following ''dah''.

Users accustomed to one mode may find it difficult to adapt to the other, so most modern keyers allow selection of the desired mode.

==== Mode {{sc|U}} ====
A third electronic keyer mode useful with a dual paddle is the "Ultimatic" mode (mode&nbsp;{{sc|U}}), so-called for the brand name of the electronic keyer that introduced it. In the Ultimatic keying mode, the keyer will switch to the opposite element if the second lever is pressed before the first is released (that is, squeezed).