  Many physics departments around the world have electronic and mechanical
workshops attached to them. The job of these workshops is to design and build
experimental setups and instruments for research and the training of
undergraduate students.
  However, in developing countries such as Sudan the lack of qualified
technicians and adequately equipped workshops hampered efforts by these
departments to supplement their laboratories with home built equipment. The
only other option is to buy needed equipment and experimental setups from
specialized manufactures. The latter option is not feasible the departments in
developing countries where funding for education and research is scarce and
very limited as equipments from these manufactures are typically too expensive.
  In the past couple of years and with the advancement in prototyping tools
like Arduino, and microcontroller development boards, more friendly programming
languages, 3D printers, desktop CNC machines and easy to use CAD/CAM softwares
the need for highly qualified technicians and expensive workshop equipment was
then relaxed \cite{nature-flypi}. The availability of such affordable, and
relatively easy to use tools had the effect of increasing the number of
teachers and researchers willing to develop their own experimental
setups\cite{polis-flypi}.
  During the past year and motivated by the need to equip our laboratories with
new setups we established a small workshop at the Department of Physics for
developing experimental setups to be used in our undergraduate laboratories.
The ultrasonic signal generator we are describing here is one such equipment.
