morse code and enabing technology

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Authors: Jeremy Cribb and Doug Daniell
This site is for a course project in Comp190/290, an Enabling Technology course taught by Gary Bishop during Spring 2003 at the UNC-Chapel Hill Computer Science Dept.
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Comp 190

The goal of this class is to educate technically-minded students in the types of disabilities that exist and the ways in which modern tools can be used to assist people with disabilities. The focus is on first-hand lectures from professionals in enabling technology, along with group research projects.

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Learn About Morse Code


Morse code: Etymology: Samuel F. B. Morse, Date: 1867 - either of two codes consisting of variously spaced dots and dashes or long and short sounds used for transmitting messages by audible or visual signals [Merriam Webster Dictionary]


As the definition indicates, Samuel Morse created Morse Code in the mid-1800s as a method for long-distance communication. He came up with the idea while a professor in New York City. It was based on the realization that sending pulses to an electromagnet could be used to transmit signals along a wire. Realing the potential for this device, Morse designed a code that would allow all of the letters and characters to be written using only these on/off pulses.

Public support was initially rather sparse. While the first demonstration was in 1938, he was not able to achieve a more comprehensive test until Congress appropriated funds in 1943. These were for the construction of a telegraph line between Baltimore and Washington. In 1944 Morse demonstrated his system with the very first message, "What hath God wraught?"

In this original system the dits and dahs were read and transcribed by a machine, to be translated by an operator later. It was later modified to allow operators to receive messages as auditory signals. As the technology improved, companies began to utilize the commercial potential of telegraphs. Western Union was formed in 1851 and had built a transcontinental line within 10 years. From there, Morse Code just continued to grow, at least until the development of the telephone. Until very recently though, Morse Code has been present at least in certain applications.


The entire system is timing based. The basic unit is the dit, which occurs when the switch is depressed for a single tick. A dah takes 3 ticks. The pause between dits and dahs is a single tick, while the space between words is 3 ticks. The sentence delimiter is twice that. All of this requires very careful timing for the message to be understood.

Once the language of the code was established, each letter and symbol that one might want to transmit was encoded. This was done by giving each unique regular symbol, 'H' for instance, a series of dits and dahs to represent it - '....'. The longest letters are composed of at most 4 symbols. For a complete list look at this table.

One key feature of the language is that it appropriates the shortest codes for the most commonly used letters. For instance, the two most common letters in general English are E and T. Sure enough, E is represented by a single dit ('.') and T by a single dah ('-'). This is very intentional, because it greatly speeds up sending common phrases. The most complex codes, with dits and dahs interspersed, are reserved for rarely used letters.