Radio Design Labs RU-ASX4DR Remote Controlled Stereo Audio Selector with VCA 4x1Features: Remote Controlled Switching and Level Control; Multiple Remote Control Locations Possible; 4 Stereo Inputs to 1 Stereo Output; Line-Level Audio Switching; External Level Control Using 10 kΩ Potentiometer or 0 to 10 Vdc; 96 dB Attenuation Range in 0.5 dB Steps; Noiseless Zero-Crossing Adjustment Steps; Precise Level Tracking on Each Channel; Balanced or Unbalanced Inputs and Output; Gain Trim on Each Source; Controllable Using Various RDL Remote Controls; Open-Collector Output for Selected Input; Specifications: Audio Inputs (4): Stereo, Line level on Detachable Terminal Block ; Input Impedance: 10 kΩ unbalanced; Input Level (for +4 dBu output): -15 dBV to +8 dBu, adjustable on rear-panel trimmers; Maximum Input Level: +25 dBu; Common Mode Rejection: 60 dB (50 Hz to 120 Hz); Headroom (above +4 dBu): 18 dB (unity gain); Frequency Response: 10 Hz to 20 kHz (±0.2 dB); Distortion (THD + N): <0.01% (20 Hz to 20 kHz); Noise (below +4 dBu): <-85 dB (with any input selected); <-95 dB (with no input selected); Off Attenuation: 70 dB (20 kHz); Crosstalk: <-80 dB (1 kHz); <-60 dB (20 kHz); Front-Panel Indicators (11): Power, Selected channel (4), VCA activity up/down (2), L and R Dual-LED VU meters (4); Audio Output: Stereo, Line level on Detachable Terminal Block; Output Impedance: 150 Ω balanced, 75 Ω unbalanced; Output Level: +4 dBu balanced, unbalanced output 6 dB below balanced output level; Control inputs (6): 1 mA, pulled to ground (4, source selection); 1 mA, pulled to +15 Vdc (SEL); 0 to 10 Vdc (VCA); Control outputs (5): 25 mA, open-collector to ground; VCA Control Input: 0 to 10 Vdc; or 0 to 10 kΩ linear potentiometer; Rear-Panel Indicators (4): L and R Dual-LED VU meters; RDL Remote Control Compatibility: D-RC4M, D-RCS4 (source selection); D-RLC10, D-RLC10M, D-RLC10K, D-RLC10KM, D-RLC3 (VCA); Power Co