title: Telephone transmission of 20-channel digital electroencephalogram using lossless data compression.
abstract: BACKGROUND
  The use of telecommunications for computer-assisted transmission of neurophysiological signals is a relatively new practice. With the development of digital technology, it is now possible to record electroencephalograms (EEGs) in digital form. Previous reports have demonstrated the possibility of real-time telephone transmission of a limited number of EEG channels.
  
  
  OBJECTIVE
  To assess the effectiveness of specific data-compression software to improve the transmission of digital 20-channel EEG records over ordinary public telephone lines.
  
  
  METHODS
  A prototype system was built to transmit digital EEG signals from one computer to another using two 14.4-kbps modems and proprietary lossless data-compression software.
  
  
  RESULTS
  Forty compressed digital EEG records of 20 channels each were sent from different locations at variable distances using "plain old telephone service" (POTS). The mean compression ratio was 2.2 to 2.8:1 using a sampling frequency of 128 Hz and 2.8:1 at a sampling rate of 256 Hz. Transmission time was reduced proportionately.
  
  
  CONCLUSIONS
  Although this study used a store-and-forward approach, the results suggest that it may be possible to transmit a large number of compressed EEG channels in real time using data compression.
authors.affiliation: Division of Neurology, S. Chiara Hospital, Trento, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Rozza
authors.forename: P
authors.initials: P
authors.lastname: Tonella
authors.forename: C
authors.initials: C
authors.lastname: Bertamini
authors.forename: D
authors.initials: D
authors.lastname: Orrico
authors.forename: G
authors.initials: G
authors.lastname: Antoniol
authors.forename: L
authors.initials: L
authors.lastname: Castellaro
mesh_terms: D004569:Electroencephalography; D005069:Evaluation Studies as Topic; D006801:Humans; D012815:Signal Processing, Computer-Assisted; D017216:Telemedicine; D013689:Telephone