In order to read the data into IDL session, give the file name as follows: 
  IDL>  file='./ds940220' 
  IDL>  nors_rd_dat,file,time,mvd,freq,datalo,datahi,mvdd2,freqd2,datad2 
 
CR
 
In order to read the data in specified duration: 
  IDL>  timerange=['1994-2-20 2:00','1994-2-20 4:00']  
CR
 
  IDL>  nors_rd_dat,file,time,mvd,freq,datalo,datahi
,mvdd2,freqd2,datad2,timerange=timerange  
CR