http://www.speedskating.ca/spectator-guide-short-track.cfm#Relay
Relay Races
Relay races normally involve four teams of four skaters per race. Each skater must take at least one turn out on the track. Normally, the skaters will exchange turns in rotation, with those not on the track either resting, covering the skater on the track, or preparing to receive a relay, all on the inside of the track. Instead of passing a baton, the skater on the track needs to only tag the incoming skater to complete an exchange. However, in order to maintain momentum, it is more common for the incoming skater to crouch and receive a push from behind. In the event of a fall, a covering skater may tag the fallen skater and continue the race. A gun will sound indicating three laps remaining, which means that each team may only complete one more exchange. One skater must complete the final two laps, except if the skater falls.