IT'S THE ULTIMATE

At first glance, you might well ask, "Ultimate what?"
[click for a much larger version] The "73" Ultimate Telegraph Transmitter, is what; more familiarly, a telegraph key. This company built a dizzying array of versions and sizes, from fancy all-chrome versions with a high degree of fit and finish to lower-priced amateur editions with exactly enough hand finishing to function. The majority of them were squarish (like mine) and came with a nice metal cover (missing from mine). They used at least two different operating mechanisms, with the one shown above being a little more common. They are very small -- 2-1/8" by 3-3/8" is typical, though at least one was much smaller. And it is the amateur version, solid but a little rough.

Mine has two levers; not all of these keys do. The right-hand one is moved to the left and makes a simple contact closure. The left-hand, moved to the left, does the exact same thing. So why's the other one there? I don't know.

The fun begins when you move the left-hand lever to the right. That's where the semiautomatic action starts to make the "dits" (usually written as "dots") for you. Like most other bug keys, it uses a weighted pendulum and a flat spring or reed to bounce back and forth; but the way this key shoves the pendulum into motion is madly complex, a square ascending spiral involving three levers, two pivots and a roller! I've tried to trace it:
[click for a larger version] Start by finding the pendulum; it runs left to right across the center of the key. Got it? That's where we'll end up. Now, move your attention to the black fingerpiece at the very bottom; the pink arrow shows what direction you'd move it. From there on up and around, the fuzzy yellow line follows the mechanism and the pink arrows show direction of movement, The lever attached to the fingerpiece moves a second lever (which it pivots away from if you moved the fingerpiece the other way but they move together in this direction); the second lever is pivoted and at its far upper end, it pushes a roller to the left. The roller is in one end of another lever shaped like a squared-off "C" and the bottom of it holds the reed and pendulum. The C-shaped lever is pivoted at its bottom left corner and thus, when the upper end is moved, the bottom end moves away from you, bumps into a stop screw and -- at last! -- the pendulum begins to vibrate. There's a little electrical contact on the pendulum arm, on its own flat, U-shaped spring, which is what actually makes the dit. Whew! When you let go, a little spring next to the stop screw pushes everything back to the at rest position.
And if you weren't confused enough, here's a back view that shows the around-two-corners lever a little more clearly.

I first saw one of these keys in 1996 at a railroad museum in French Lick, Indiana; it was in a display case and I was unable to get a clear enough look at it to figure out how it worked. I've wanted one ever since.

Photo links are from this page at Tom Perera's online museum, where a key-fancier can easily spend hours. I was able to find a few more examples via a websearch as well.