Editing Keyer (section)

=== History & telegraphy background ===
In [[telegraphy]], so-called [[Telegraph key#Dual-lever paddles|''iambic'' keys]] developed out of an earlier generation of novel side-to-side, double-contact keys (called "bushwhackers") and later, mechanical semi-automatic keys (called "bugs"). Semi-automatic keys were an innovation that had an impulse driven, horizontal pendulum mechanism that (only) created a series of correctly timed [[Morse code|"dits"]]. The pendulum would repeatedly tap a switch contact for as long as its control lever was held to the right (or until the impulse from the thumb push was exhausted); telegraphers were obliged to time the [[Morse code|"dahs"]] themselves, by pressing the lever to the left with their knuckle, one press per "dah". When the lever is released, springs push it back to center, break the switch contact, and halt and reset the pendulum. Because the "dits" are created automatically by the pendulum mechanism, but the "dahs" are keyed the old-fashioned way, the keys are called "''semi''-automatic". (Modern electronic keyers create both the "dits" and the "dahs" automatically, as long as one of the switches is in contact, and are called "''fully''-automatic".)

More than just convenience, the keys were needed for medical reasons: Telegraphers would often develop a form of [[repetitive stress injury]], which at that time was called "[[glass arm]]" by telegraphers, or "telegraphers’ paralysis" in medical literature. It was common and was caused by forcefully "pounding brass" up-and-down on conventional telegraph keys. Keys built for side-to-side motion would neither cause nor aggravate the injury, and allowed disabled telegraphers to continue in their profession.