Telex Integrated Signal Processor ISP-100 - Manual (Page 120)

8-50
10 July 1998
Computation of Average Level
There are two common methods of computing average signal
level; one is based upon RMS (Root Mean Square) calculations,
and the other is based upon Absolute Value calculations. Each
of these methods produces a slightly different value for signal
level, and the difference depends upon the characteristics of the
signal itself. The ISP-100 limiter uses Absolute Value for its
computation of signal level, so the level reported by the limiter
may differ slightly from the RMS value expected for a given
signal.
Crest Factor Sensitivity and Sinewaves
The peak level of a pure sinewave tone is 1.414 times its
average level. The ISP-100 limiter will therefore apply
approximately 3 dB more limiting to a pure sinewave signal
when the Crest Factor Sensitivity is set to 1.00 (peak-
responding) than when it is set to 0.00 (average-responding).
This represents normal operation for the limiter.
Sidechaining
When the sidechain source for an ISP-100 limiter is selected to
be a channel other than its own input, the limiter controls must
still be set. The sidechain selects only the channel’s data, not its
limiter control settings. If multiple limiters utilize the same
channel as their sidechain sources, then all controls on all
limiters must still be configured.
Meter
The meter located at the left of the component indicates the amount
of attenuation taking place in dB.
Threshold
The Threshold can be adjusted three ways:
Using the Slider
Click on the indicator on the slider and while continuing to hold
down the mouse button, move the mouse up and down. The
numbers in the box below the slider will change. When the
desired level is reached, release the mouse button.
Using the Text Box
Click in the box. Using the Back Space and/or Delete keys
erases the current entry and enters the new level. Be sure to
press the Enter key after the entry is made. Clicking outside the
text box without pressing the Enter key will cause the setting to
return to the number that it was before a change was attempted.
Alternatively, click and drag across the number in the box to
highlight the number in it. Type the new setting and press the
Enter key when finished.
Using the UP/DOWN Arrows
To increase the level, click on the up arrow. To decrease the
level attenuation, click on the down arrow. The amount of