The AD903 allows the connection of almost any other audio device, input or output, to a cabled intercom system. Typical applications include: 1) feeding the signal from a stage microphone or audio mixer output into the intercom system so that intercom users can monitor the program from a distant point; 2) feeding the intercom conversations out to an audio amplifier, and; 3) connecting the intercom system to another intercom system which is operating on a different voltage or standard.

The AD903 is connected into the intercom system as is a belt pack, via the 3-pin female XLR on the rear. A 3-pin male XLR is provided for looping onwards to the next station in the system. The AD903 is powered by the intercom power supply. Input and output are accessed via the 4-pin male XLR, also on the rear panel. Front panel high/low switches and 15-turn potentiometers allow the user to level-match virtually any input or output, from microphone level to line level. A third potentiometer is used to null the sidetone effect, reducing cross-talk.

The input stage of the AD903 includes a studio-quality microphone transformer. The output is also transformer isolated. Frequency response has be carefully shaped to optimize both intelligibility and long-term listening comfort.

The ribbed, extruded aluminum case; polypropylene end bezels; internal support system for the PC board; carefully mounted components; best-quality XLR-type connectors, and; recessed controls, all contribute to the outstanding ability of the AD903 to withstand rough usage.

The comparatively low price of the AD903 is made possible by the minimized assembly cost, resulting from simplicity of construction. Simple construction also affords the use of higher quality components, and increases the ease (thus lowering the cost) of servicing.