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1.                 From The Free On-line Dictionary of Computing (19 January 2023):
                   
   
   
                   
                     
   External Machine Interface
   EMI
      <protocol> (EMI) A protocol primarily used to connect to
      short message service centres for mobile telephones.  EMI
      is an extension to Universal Computer Protocol (UCP).  EMI was
      was developed by CMG, now a part of LogicaCMG, the current
      SMSC market leader.
      Each byte of the message is encoded as two hexadecimal
      characters using an encoding not quite like ASCII.
      EMI specification
    (http://www.netfunitalia.it/downloads/SMSCEMISpecification.PDF)
      (2007-09-10)