I'll answer this quick before Larry J. beats me to it. The SR-71 used conventional ejection seats. The pilot and the guy in the back seat (not a co-pilot but rather a RIO(?) or Recon. Intelligence Officer(?)) wore pressures suits just like the ones used by the astronauts of the Space Shuttle for ascent and descent. The pressure suits were developed for the SR-71 by the Air Force and then NASA made use of the same design for the Shuttle. The ejection system for the SR-71 was automatic.

Here's a story told to me years ago by an SR-71 aircraft mechanic while standing under an SR-71B at Beale Air Force Base. Two guys were flying at Mach 3+ in an SR-71 over the Pacific Ocean. One of the engines unstarted and the SR-71 immediately went into a flat spin. The SR-71 disintegrated around the pilot while he was losing consciousness. The ejection system engaged automaticly and ejected the unconscious pilot from the disintegrating wreck. After being ejected, the parachute deployed automaticly and the still unconscious pilot descended into the ocean. After landing in the ocean, a floatation device deployed automaticly along with a beacon radio. The pilot came-to while floating in the ocean as a helicopter was coming to rescue him. The RIO was less fortunate and disintegrated with the SR-71.

Gary