Telegraph key

A straight key is the common telegraph key as seen in various movies. It is a simple bar with a knob on top and an electrical contact underneath. When the bar is pressed down against spring tension, it makes a closed electric circuit. Traditionally, American telegraph keys had flat topped knobs and narrow bars (frequently curved), while British telegraph keys had ball shaped knobs and thick bars. This appears to be purely a matter of culture and training, but the users of each are tremendously partisan.[lower-alpha 1]

Straight keys have been made in numerous variations for over 150 years and in numerous countries. They are the subject of an avid community of key collectors. The straight keys used in wire telegraphy also had a shorting bar that closed the electrical circuit when the operator was not actively sending messages. This was to complete the electrical path to the next station so that its sounder would operate, as in the operator receiving a message from the next town. Although occasionally included in later keys for reasons of tradition, the shorting bar is unnecessary for radio telegraphy, except as a convenience when tuning the transmitter.

The straight key is simple and reliable, but the rapid pumping action needed to send a string of dots (or dits as most operators call them) poses some significant drawbacks.

Transmission speeds vary from 5 words (25 characters) per minute, by novice operators, up to about 30 words (150 characters) per minute by skilled operators. In the early days of telegraphy, a number of professional telegraphers developed a repetitive stress injury known as glass arm or telegrapher's paralysis. "Glass arm" or "telegrapher's paralysis" may be reduced or eliminated by increasing the side play of the straight key by loosening the adjustable trunnion screws. Such problems can be avoided by using a good technique.[1][2][3]

In addition to the basic up-and-down telegraph key, telegraphers have been experimenting with alternate key designs from the beginning of telegraphy. Many are made to move side-to-side instead of up-and-down. Some of the designs, such as sideswipers (or bushwhackers) and semi-automatic keys operate mechanically.

Beginning in the mid-20th century electronic devices called "keyers" have been developed, which are operated by special keys of various designs generally categorized as single-paddle keys (also called sideswipers), and double-paddle keys (or "iambic"[lower-alpha 2] or "squeeze" keys). The keyer may be either an independent device that attaches to the transmitter in place of a telegraph key, or circuitry incorporated in modern amateurs' radios.

The first widely accepted alternative key was the sideswiper or sidewinder, sometimes called a cootie key or bushwhacker. This key uses a side-to-side action with contacts on both the left and right and the arm spring-loaded to return to center; the operator may make a dit or dah by swinging the lever in either direction. A series of dits can be sent by rocking the arm back and forth.

This first new style of key was introduced in part to increase speed of sending, but more importantly to reduce the repetitive strain injury affecting telegraphers, then popularly called "glass arm" or clinically "telegraphic paralysis". The side-to-side motion reduces strain, and uses different muscles than the up-and-down motion (called "pounding brass"). Nearly all advanced keys use some form of side-to-side action.

The alternating action produces a distinctive rhythm or swing which noticeably affects the operator's transmission rhythm (known as his ‘fist’). Although the original sideswiper is now rarely seen or used, when the left and right contacts are electrically separated a sideswiper becomes a modern single-paddle key (see below); likewise, a modern single-lever key becomes an old-style sideswiper when its two contacts are wired together.

Early "bug" telegraph key invented in 1913 by Weston Hadden

A popular side-to-side key is the semi-automatic key or bug, sometimes known as a Vibroplex key, after the company that first manufactured them. The original bugs were fully mechanical, based on a kind of simple clockwork mechanism, and required no electronic keyer. A skilled operator can achieve sending speeds in excess of 40 words per minute with a ‘bug’.

The benefit of the clockwork mechanism is that it reduces the motion required from the telegrapher's hand, which provides greater speed of sending, and it produces uniformly timed dits (dots, or short pulses) and maintains constant rhythm; consistent timing and rhythm are crucial for decoding the signal on the other end of the telegraph line.

The single paddle is held between the knuckle and the thumb of the right hand. When the paddle is pressed to the right (with the thumb), it kicks a horizontal pendulum which then rocks against the contact point, sending a series of short pulses (dits or dots) at a speed which is controlled by the pendulum’s length. When the paddle is pressed toward the left (with the knuckle) it makes a continuous contact suitable for sending dahs (dashes); the telegrapher remains responsible for timing of the dahs.

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 "iambic"[lower-alpha 2] 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 iambs in poetry.[5][6] 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 trochees in poetry, and the method could as logically be called "trochaic keying" (  ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄  ...). If the dit lever makes first contact, then the string begins with a dit (  ▄ ▄▄▄ ▄ ▄▄▄ ▄  ...).

Insofar as iambic[lower-alpha 2] 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 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 C (dah-dit-dah-dit   ▄▄▄ ▄ ▄▄▄ ▄ ).

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.[7]

Iambic keyers function in one of at least two major modes: Mode A and mode B. There is a third, rarely available mode U.

Mode A is the original iambic mode, in which alternate dots and dashes are produced as long as both paddles are depressed. Mode 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 B is the second mode, which devolved from a logic error in an early iambic keyer. Over the years iambic mode B has become something of a standard and is the default setting in most keyers.

In mode 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.

A third electronic keyer mode useful with a dual paddle is the "Ultimatic" mode (mode 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).

A single-lever paddle key has separate contacts for dits and dahs, but there is no ability to make both contacts simultaneously by squeezing the paddles together for iambic mode.

When a single-paddle key is used with an electronic keyer, continuous dits are created by holding the dit-side paddle (  ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄ ...); likewise, continuous dahs are created by holding the dah paddle (  ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ...). A single-paddle key can non-iambicly operate any electronic keyer, whether or not it offers iambic functions, and regardless of whether the keyer operates in iambic mode A, B, or U.