  The transmission rate of communication between radio telescopes on Earth and
extraterrestrial intelligence (ETI) is here calculated up to distances of 1000
light years. Both phase-shift-keying (PSK) and frequency-shift keying (FSK)
modulation schemes are considered. It is shown that M-ary FSK is advantageous
in terms of energy. Narrow-band pulses scattered over the spectrum sharing a
common drift rate can be the probable signals of ETI. Modern SETI spectrum
analyzers are well suited to searching for these types of signals. Such signals
can be detected using the Hough transform which is a dedicated tool for
detecting patterns in an image. The time-frequency plane representing the power
output of the spectrum analyzer during the search for ETI gives an image from
which the Hough transform (HT) can detect signal patterns with frequency drift.
