The portable RF transmitter shall be capable of broadcasting on 32 channels. The unit shall incorporate a microphone sensitivity switch. The device shall broadcast on both wide and narrow band channels with a SNR of 80 dB or greater. The device shall have an audio frequency response of 50 Hz to 15 KHz (‘±3 dB). The device will incorporate a mute switch. The battery door shall be capable of being mechanically locked. The device shall incorporate an LCD display that indicates channel, battery level, low battery, battery charging, and RF signal strength. The device shall be able to enable companding. The unit shall operate off of two (2) AA batteries; alkaline or NiMH. The portable transmitter shall incorporate automatic battery charging circuitry for recharging of NiMH batteries, with the ability to charge via a wall transformer or drop in charging case. The Listen LT-700-150 is specified.