Those go to a circuit board he designed which modulates the carrier with the audio signal using a single transistor and then sends the result out the ultrasonic transmitter.

You’ll also have to learn Morse code because the minimalist build only supports continuous-wave (CW) mode, although it can be modified for amplitude modulation (AM) voice work.

Chemical bath deposition was used to grow polycrystalline thin films of CdS on glass substrates. During the process of growth relative volumes of nitrate of erbium penta-hydrate (Er(NO3)35H2O). The Er ...