The 5-level baudot code was devised to permit teletypewriter to operate faster and more accurately than relays used to transmit information via telegraph. Since the number of different characters which can be derived from a code having two different (binary) states is 2^m,where m is the number of position in the code, the 5-level Baudot code permits 32 unique character bit combinations. Although 32 characters could be represented normally with such a code, the necessity to transmit digits, letters of the alphabet and punctuation marks made it necessary to devise a mechanism to extend the capacity of the code to include additional character representations. The extension mechanism was accomplished by the use of two ‘shift’ characters-‘letters shift’ and ‘figures shift’. The transmission of a shift character informs the receiver that the characters which follow the shift character should be interpreted as characters from a sysbol and numeric set or from the alphabetic set of characters. The 5-level Baudot code is illustrated in figure 2.1 for one particular terminal pallet arrangement. A transmission of all ls in bit positions l to 5 indicates a ‘letters shift’ and the characters following the transmission of that character are interpreted as letters. Similarly, the transmission of ls in bit positions 1,2,4 and 5 would indicate a ‘figuers shift’ and the following characters would be interpreted as numeric or sysbols based upon their code structure.