The TSD-PA20VG is a cost effective mono amplifier for 4 ohms and distributed constant voltage speaker systems.Applications include hallways and classrooms.The TSD-PA20VG is also a cost effective alternative for small projector systems as it can be used with as many as (16) 25/70/100V ceiling speakers (tapped at 1W each), plus the extremely small footprint allows for easy mounting.For sound masking applications the TSD-PA20VG has the capacity to drive up to 34 masking speakers tapped at .5W each on a 70.7V line.Output is gain controlled from a potentiometer on the front panel with removable knob.