These pocket telegraph sets were built by David Harbin. They are modeled after those used in the Civil War.
The case is Walnut. The cases that have survived are usually hard rubber or of pasteboard design.
The coil resistance of set number two, owned by David Harbin, is 200 ohms. Set number one, in the OVCWA inventory, is 50 ohms.
As such, it operates quite snappily on twelve (or less--little "soft" at six volts drop) volts at a maximum current draw of about 250 milliamperes. The 200 ohm version
works nicely at about 30-32 volts with a current draw of about 70 milliamperes. These instruments can be configured for
50, 100, 200, 400 or 800 ohms by merely changing the wire configuration of the coils. This means that they can be made to
function well on most any line and voltage available.
These pocket sets are similar to a Confederate pocket telegraph used during the Civil War. Contrast this design with the instruments
used late in the Civil War by the Union as shown by Plum's pocket set.
Not all operators had pocket sets. However, an attempt was made to provide each operator with one. Whether they were issue
or the operator was required to purchase his own set is not yet known.