Sony M-425 Operating Instructions Manual page 6

Recording cue markers (M-727V only)
While recording, you can record a special signal on the
tape to mark a specific position.
At the desired position, press CUE MARKER to record a
signal. The REC/BATT lamp goes off and a signal will be
recorded on the tape. If you want to record a signal
longer than that, press CUE MARKER as long as you
want.
During cue and review, you will hear the beep sound at
the signal position. During playback, you will hear the
signal with low frequency sound at the signal position.
Notes
©We recommend recording cue markers when there is a break in
. the sound.
.,¢ During cue and review, the beep sounds differently.
¢ The beep may sound differently depending on the marked
position on the tape because the winding speed varies from the
beginning to the end of the tape.