The PST-170 belt pack transmitter may be set to any one of the 17 channels, and operates on frequencies in the 72-76 MHz band. It is lightweight, battery operated and includes a small electric lapel microphone for convenient portable use. The PST-170 has two audio input jacks. The Auxiliary input is designed to allow audio devices such as teacher's aids or tape players. The second jack is normally used for microphone and is located on the top panel. The channel is displayed on a backlit LCD and can be locked to prevent accidental changes. The PST-170 also includes the E.D.R. feature for improved sound quality and intelligibility.