Returns the type  of the channel 'num' based 
        on its unit stored in the Comtrade header file.
        
        Returns 'V' for a voltage channel and 'I' for a current channel.

def getAnalogType(self,num):
        """
        Returns the type  of the channel 'num' based 
        on its unit stored in the Comtrade header file.
        
        Returns 'V' for a voltage channel and 'I' for a current channel.
        """
        listidx = self.An.index(num)
        unit = self.uu[listidx]

        if unit == 'kV' or unit == 'V':
            return 'V'
        elif unit == 'A' or unit == 'kA':
            return 'I'
        else:
            print 'Unknown channel type'
            return 0