Dunn Patent Bugs

(Dunduplex & National Upright)

Thomas Dunn, from Jersey City, NJ designed some very interesting bugs.

His most well known key is the Dunduplex which came in both single-lever and double-lever models. The double-lever model was his first design and also the scarcer of the two. The key operates in two ways. First, the key can be operated like a normal semi-automatic key by moving the paddle(s) from side to side. Or, the operator can depress the two black plungers on top of the frame to produce the dots and dashes.

Dunn's other key was a vertical pendulum design, similar to the Vibroplex Upright, that he sold through his outfit called The National Transmitter Co, also in Jersey City. There were 2 versions of the National Upright bug. Both operated similarly but one was larger than the other.

Links to the patents for each key can be found at the bottom of this page.

(Click on the pictures below to see larger versions of the photo)


Double Lever Dunduplex


This is the double-lever Dunduplex. Note the black plungers on top of the frame that are marked with a dot or dash symbol. The "Dash" plunger operates like a simple hand key, while the "Dot" plunger actually causes the pendulum to move just as if the dot paddle was moved. The Dunduplex came with a unique metal carrying case that was shaped like a mailbox.


Single Lever Dunduplex (First Version)


The single-lever Dunduplex was Dunn's second design. As with the double-lever design, this key also had 2 black plungers as an optional way to operate the key.


Single Lever Dunduplex (2nd Version)


Later, Dunn changed the design of the single-lever key to eliminate the plungers. The problem with the plungers is that they could fall out of the key if it was turned upside down. It is not uncommon to see Dunduplex bugs that are missing one or both plungers. So the plungers were replaced with knurled thumbscrews which accomplished the same thing.


National Transmitter Co. Vertical Bug (Small Version)


Here is a nice example of Dunn's first version of the National Transmitter Upright bug. It is quite a small key but takes very little force to operate, so despite its small size, it does not move around on the operator's desk.


National Transmitter Co. (Large Version)


Dunn's second version of the bug was larger than the first, but operates the same way. On the right is a picture that shows both versions.




National Transmitter Upright