The RU-ASX4D is a four channel stereo audio selector with input gain adjustments and output level metering. The inputs and outputs are connected on rear-panel detachable terminal blocks.

Each of the four stereo line level inputs accepts either a balanced or an unbalanced signal. Each input is equipped with a rear panel screwdriver-adjustable input gain trimmer. Input signal levels between -15 dBV and +8 dBu may be set to the proper operating level as indicated by a stereo dual-LED VU meter. This assures ample headroom at all normal operating levels. The module is equipped with two identical dual-led VU meters, one on the front panel, the other on the rear panel. The maximum input level is +25 dBu.

The RU-ASX4D was designed for absolute silent switching of audio signals using only solid-state switching circuitry.

The output is stereo line level. Each output channel may be connected balanced or unbalanced. Each of the VU-meters, left and right, is calibrated to read +4 dBu for the corresponding balanced output.

A front-panel LOCAL/REMOTE switch enables either the front-panel buttons or the rear-panel remote control terminals provided on detachable terminal blocks. In the LOCAL mode, four keyboard style long-life pushbuttons on the front panel are used to select one input. When a button is pushed, the corresponding audio input is fed to the output and any previously selected source is shut off. Only one source may be selected at a time. If the button for a selected source is pushed again, all inputs are turned off. An LED above each pushbutton indicates the selected source. In the REMOTE mode, inputs are selected by a sequential remote control such as an RDL D-RCS4, by a momentary remote control such as an RDL D-RC4M or by an external open-collector momentary closure to ground. The RU-ASX4D may be remote controlled from a single or from multiple locations. When a source is selected, the RU-ASX4D provides a 25 mA open-collector output to control other equipment or modules.

Rear-panel DIP switches are provided to permanently activate the remote control terminals, to select the remote control mode (sequential or individual source selection), and upon power-up a return to either a pre-programmed source or to the last source used. The pre-programmed source is stored when the module is installed.

The RU-ASX4D offers exceptional headroom, very low distortion, excellent crosstalk isolation, wide flat frequency response and extremely low noise with very high common-mode signal rejection. It provides exceptional audio performance for the most critical applications in a professional audio environment.

The RU-ASX4D operates from 24 Vdc connected through a rear-panel detachable terminal block.