The device ... slides snugly deep into the bugle's bell. The device plays a high-quality recorded version of “Taps,” taken from the 1999 Memorial Day service at Arlington National Cemetery. The resonating tones inside the bugle create a realistic horn quality.And here's a related article:
"Facing critical shortage of musicians for military funerals, the Pentagon has approved the use of a push-button bugle that plays taps by itself as the player holds it to his lips"Link (Thanks, Simon!)
..."With a small digital recording devise inserted into each bugle's bell, a member of the honor guard at the funeral simply presses a button on the devise. A five-second delay give the guards time to raise the instrument to their lips as if they are going to play it"