Telegraph key
From Wikipedia, the free encyclopedia
Telegraph key, also known as a Morse key, are generic terms for any switching device used primarily to send Morse code. Similar keys are used for all forms of manual telegraphy, such as in electrical telegraph and radio telegraphy.
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[edit] Types of keys
Since its original inception, the telegraph key's design has developed such that there are now multiple types of keys.
[edit] Straight keys
A straight key is the common telegraph key seen in old movies. It is a simple bar with a knob on top and a contact underneath. When the bar is depressed against spring tension, it forms a circuit and allows electricity to flow. Traditionally, American telegraph keys had flat topped knobs and narrow bars (frequently curved.) 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.
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 are limited to around 20 words per minute, and in the early days of telegraphy a number of professional telegraphers developed a repetitive stress injury known as glass arm or telegrapher's paralysis.
[edit] Alternative key designs
The first widely accepted alternative key was the sideswiper or sidewinder, sometimes called a cootie key. This key uses a side-to-side action with contacts in both directions and the arm spring-loaded to return to center. A series of dits could be sent by rocking the arm back and forth. The alternating action produces a distinctive rhythm or swing which contributes noticeably to the the user's fist. Although the sideswiper is seldom seen or used today, nearly all advanced keys use some form of side-to-side action.
A popular side-to-side mechanical key is the semi-automatic key or bug, sometimes known as a Vibroplex key, after the company that first manufactured them. When the paddle is pressed to the left it makes a continuous contact suitable for sending dashes (or dahs, as most operators call them). When the paddle is pressed to the right, a horizontal pendulum is set into motion which rocks against the contact points, sending a series of short pulses (dits) at a speed which is controlled by the position of the pendulum weight. A skilled operator can achieve sending speeds in excess of 40 words per minute with a bug.
Like the bug, the electronic keyer operates sideways. When pressed to one side the electronics generate a series of "dahs" and when pressed the other way, a series of "dits". Most electronic keyers include a dit memory function which frees the operator from the need to perfectly time his transitions in the sequence dah-dit-dah. With dit memory, if the operator's keying action is about one dit ahead of the actual transmission, the keyer's output for each letter will be machine-perfect. An iambic keyer sports dual paddles, one for dit and one for dah; pressing both at the same time produces an alternating dit-dah-dit-dah sequence. Electronic keyers allow very high speed transmission of code.
[edit] Iambic (dual-lever) Paddles
Keys offering one contact for dits and another for dahs were dubbed "iambic paddles," when each contact may be closed simultaneously. The iambic function (alternating dits and dahs) are created with an electronic keyer by squeezing the paddles together.
A single-paddle also utilizes separate contacts for dits and dahs, but there is no ability to make both contacts simultaneously by squeezing the paddles together (iambic). When a single-paddle key is used with an electronic keyer, continuous dits are created by holding the dit side. Likewise, contiunous dahs are created by holding the dah contact.
Iambic keying or squeeze keying creates alternating dits and dahs. This makes sending some characters easier, like the letter "C," by merely squeezing the two paddles together. In single-paddle, non-iambic keying, the hand motion would require alternating four times for "C" (dah di dah dit).
Typically, single and dual-paddle keys use horizontal movements, while a straight-key utilizes an up an down movement.
[edit] Key's influence on sender's personal characteristics
All telegraphists unconsciously develop personal quirks, or characteristics, which collectively called one's "fist." While with any type of keyer it is easy to send a jerky or "choppy" code, as well as to make inconsistently longer or shorter dits or dahs overall or in certain characters, the type of key in use may greatly influence one's sending as it sounds to the receiving operator. A common fault with using a semi-automatic key is to make the dits too fast as compared with the dahs. Sideswipers tend to encourage to some very oddly timed characters and inconsistent formations.[1]
[edit] Non-telegraphy uses of keys
Telegraph keys were once used in the study of operant conditioning with pigeons. Starting in the 1940s, initiated by B. F. Skinner at Harvard University, the keys were mounted vertically behind a small circular hole about the height of a pigeon's beak in the front wall of an operant conditioning chamber. Electromechanical recording equipment detected the closing of the switch whenever the pigeon pecked the key. Depending on the psychological questions being investigated, keypecks might have resulted in the presentation of food or other stimuli. Modern pigeon response keys are specially made switches but are still called "keys" due to their origins as telegraph keys.[citation needed]
[edit] Notes and references
- ^ Pierpont,William G. The Art & Skill of Radio-Telegraphy. Retrieved 1 April 2007
[edit] External links
- History of the Morse Key
- Virtual Vibroplex - AE4RV's Flash-based bug demonstration by
- Sparks Telegraph Key Review - A pictorial review of telegraphy and telegraph keys with an emphasis on spark (wireless) telegraphy.
- The Telegraph Office - A resource for telegraph key collectors and historians
