These devices are high voltage, high speed transistors for horizontal deflection output stages of TV's and CRT's.
High Voltage: VCEV = 330 or 400 V
Fast Switching Speed: tf = 750 ns (max)
Low Saturation Voltage: VCE(sat) = 1 V (max) @ 5 A
Datasheet Available:Motorola BU406
TO-220 package. Manufactured by Motorola.