Type I Noise Reduction 911

The 911 incorporates one channel of encode and one channel of decode circuitry in the dbx® Type I format. The Type I system doubles (up to a maximum of 115 dB) the dynamic range of the storage or transmission medium. This is achieved through compressing the signal by a 2:1 ratio during record then expanding the signal 1:2 with a precisely complementary deemphasis during playback. The companding is linear over a 100 dB range. It requires no pilot tones or special calibration. 

Type I provides best results when used with transmission or storage media exhibiting flat frequency response (±1 dB 20 Hz - 20 kHz) - typically open reel recorders running at 15 or 30 ips, or digital media. The signal's dynamic range is cut in half, with the hottest levels considerably reduced and the softest passages boosted. On decoding, the signal is precisely expanded back, and the original dynamic range of the program is retrieved without hiss, saturation distortion, or degradation of frequency response. 

Industry standard Type I noise reduction.
Greater than 40dB improvement in dynamic range for typical systems.
Front panel adjustable to match facility levels from -12 to +16dBu.
Hardwire bypass switch.

Used in a DBX 900 rack adapter. The rack adapter can hold up to 9 modules, and provides DC power to each module.

Here you find 26 models, 25 with images and 4 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
All listed radios etc. from dbx Inc.; Waltham (MA)