Telex ISP-100 manual Computation of Average Level

8-50

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

10 July 1998