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Transmitter

(A) Volume Control - Controls the volume level of music transmitted
(B) Power Button
(C) Power LED
(D) Low Battery LED
(E) Audio Level LEDS - Shows Audio Level

Receiver

(A) Scan Button - Detects Transmitting Units Frequency and connects to it.
(B) Stereo LED - Lights when connected to the wireless transmission
(C) Power Button
(D) Audio Level LEDS - Shows Audio Level
(E) Low Battery LED

(A) Channel Selector - Allows you to select the frequency to transmit on
(B) Audio In - Input from soundcard
(C) Audio Out - Output to speakers
(D) Power Input

(A) Radio Frequency Selector - Allows you to select the radio frequency to broadcast on for listening through a FM radio.
(B) Audio Input
(C) Audio Input
(D) Power Input

Here is a picture of the battery compartment that is available on both units in case you dont have a power outlet available.