JBL M644 multi channel noise gate. Favorite for drums!

From JBL:
- Combines four independent channels of noise gate in a compact one rack space chassis. 
- User adjustment of Threshold, Attenuation, Attack and Release controls. 
- Increased versatility through extremely broad Threshold control range (-60 to +20 dBu). 
- Servo balanced outputs provide automatic output level adjustment to accommodate either balanced or unbalanced feeds. 
- External key inputs on each channel allows gate triggering from external sources. 
- Outstanding 115 dB dynamic range for lower noise, greater headroom, and unparalleled transient response. 
- Extremely low distortion; THD 0.03%. 
Wide bandwidth, flat response; 10 Hz to 40 kHz. 
- Subsonic filtering for protection of low frequency transducers from over excursion. 
- External ground link terminals for independent access to signal and chassis grounds, permitting greater flexibility in system grounding.