Abstract: A digital signal recording method and apparatus for recording digital signals of two channels along tracks on a magnetic tape in a helical pattern by employing at least two pairs of rotary heads mounted on a rotatable drum oppositely to each other and by making use of a read-after-write function, the paired heads being disposed adjacent to each other. The input signal to be recorded is compressed such that the digital signal recording period for each relevant track is shortened by a ratio corresponding to a time for which a write period for one track and a read period for adjacent one overlap each other. The write period and the read period are thus prevented from overlapping. The reproduced signal for the read-after-write function is prevented from being masked by an input signal recording current.

Abstract: A reader (10) capable of efficiently reading tags (12) of differing protocols in a radio frequency identification system. The tag may be either a full-duplex tag or a half-duplex tag. The reader includes a display (16), a power switch (18) and a read switch (20) for enabling operation of the reader by a user. The reader further includes a coil (60); a driver circuit (32) coupled to the coil; and a signal analyzing circuit (82, 84, 90) coupled to the coil. The signal analyzing circuit analyzes tag identification signals sensed by the coil by detecting an initial data sequence of the tag identification signals and selecting from at least two different protocols the correct protocol of the tag identification signal.