A Wasner biophaser was a rectangular, hand-held, medical instrument which was utilized by Federation doctors in the 23rd century. Essentially based on the hand phaser, the biophaser was tuned to generate heat energy instead of destructive energy. Dr. McCoy used a Wasner biophaser on Spock to raise his body temperature in 2267, after the Vulcan had been exposed to the intense cold of the dark side of the planet Rimillia. (TOS novel: Twilight's End)