Note
The HD-16 featured separate volume and tone controls, a built-in speaker, key jack, and headphone jack and flasher light (for the scouting merit badge program).
The unit replaced the older CO-1, uses a unijunction transistor, and is powered by two 9 volt transistor batteries, and one “C” cell for the light.
The HD-16 is finished in classic SB two-tone green wrinkle paint. Be sure to check for battery damage—but don’t necessarily let it stop you from buying. Assuming the outside of the unit is in good shape, the battery clips can be replaced.
Note: The 130Ω speaker would not be easy to replace.
The HD-16 was originally supplied with a key, but the key is seldom found with the units today. Replaced by the HD-1416 in 1975.
Transistor: 4JX5E670 GE unijunction
Tone frequency: 500 Hz nominal center frequency (adjustable)
Speaker: 130Ω
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
