The range of the threshold is from -30dB to 20dB. The Range control determines the attenuation of the closed gate from 0 dB to 80 dB. The attack time can be adjusted from 0.01 ms to 30 ms. With the fastest setting the audio signal is present within the first 90 degrees of a 10 kHz signal. The range of the release time is from 50 ms to 5 s; the hold control covers the same range. Hold determines the time the noise gate remains open after the input signal drops below threshold. The release time setting controls the fade out time from 0 dB with gate open to the attenuation, that is determined by the range control. The hold times delays the begin of the fade out that is depending on the release time setting.
The state of the noise gate is displayed with 3 LED's and an additional LED chain. The green open led is on if there is no attenuation; orange displays that hold time is running and the red LEDs is on when the noise gate is closed or the release fade out is in progress. The attenuation is displayed with the additional LED chain with 8 LED's.
The Filter section can be inserted into the side chain of the unit. The low pass filter has a range from off, to 500 Hz. The control range of the high pass filter is from 20 Hz to 2 kHz. The ranges can be multiplied by 0.1 for the low pass and by 10 for the high pass filter with a switch. Both the filters have a steep rate of 12 dB/oct.
The side chain input is normally connected to the audio input and can be driven from a second input is the key switch is pressed. The filter section can also be used with the key input. The SCL switch allows the control of the side chain signal and switches the input of the rectifier section post the filter to the output of the device. The GATE switch activates the whole unit, which is hard-bypassed until this switch is pressed.
The I99 Enveloper fits into every 4U high Integrator frame.