Abstract
M.Ing. (Electrical and Electronic Engineering)
Since the beginning of telecommunications. more than 100 years ago, systems have been
developed through a constant interaction between technical inventions. economic applications
and the desire for improved communication facilities to such an extend that there is now a
highly efficient communication network whichspans over the entire globe. The still growing
demand for data communication. on conventional channels such ascoaxial cables and twisted
pairs. made it necessary to develop systems which make use of line codes. In developing
countries. like South-Africa. it is not economically feasible to change the existing analog
systems to digital systems to enable data communications.
In this study. we have done research into the possibility of combining ananalog speech signal
with a digital data channel. Ideally the data channel should make use of line codes with low
power contents at low frequencies. so that an analog speech channel can be inserted.
Different coding methods were used to construct simple encoders and decoders which
generate sequences with low power content at low frequencies. The experimental setup used
in this thesis. showed that these new line codes exhibit low frequency suppression to such an
extend that an analog speech channel can be inserted without the one interfering with the
another.