Some Observations

• The telegraph is a digital transmission system.
• Information or messages are transmitted in the form of binary pulses (if we ignore the ``spaces'').
• The term ``binary'' means that there are only two basic signals that are ever transmitted: a short pulse and a long pulse.
• We will see that the similarities between the telegraph and modern, digital communication systems are quite amazing.
• The most noticeable difference is that encoding and decoding of information into binary, as well as the transmission and reception of digital information is fully automated today.
• Traditionally, the telegraph was used to transmit text.
• However, using sampling and quantization of samples (A/D conversion) any signal could be transmitted via telegraph.
• In modern, digital communication systems, a clock signal is used instead of ``spaces'' to mark the end of pulses.