Logic position on the Select-Pin mode is undertaken with the help of the 2 x 4-times sliding switch S1A, in which two diodes D1 and D2 are used for additional decod-ing. The selection of the control- D LEDs for the respective functions is made by means of S1 B, in which B9 is used for limiting the LED current.
The chip permits direct adjustment of 6 different parameters using in- tegrated DC voltage electronic potentiometer. Besides the con- tinuous adjustment of the phase shift between the foreground stereo signal and the background Sur- round-signal, the module possesses a separate loudspeaker adjustmentfor the foreground stereo channels and the center-channel in addition to a Balance, High and Low adjustments for the stereo-main-channel. The direct excitation is obtained by a controlled DC voltage in the range between O and 5 V fed to the input pins 16 to 20 and 23 of the (IC 1).
Since all the assemblies necessary for decoding the Surround-Signal are comprisedin a highly integrated chip, the internal structure of (IC 1) shown in fig.2 elucidates the method of functioning of the Surround-Decoders. The audio signals of the two stereo channels reach at first at a chip-in- ternal matrix and from there to the stages responsible for sound influ- encing as well as for sound-inten- sity and balance-adjustment. The corresponding stereo signals influ- encing the individual tastes are decoupled on pin 14 and pin 12 of the chip. By cumulating the L+Fl signals the generation of the center-channel is obtained. The cumulated signal available on pin 13 of the (IC 1) can be influenced in the sound intensity through an integrated electronic potentiometer. The decoding of the Surround-Signal forthe background loudspeaker boxes calls for a high amount in expenditure. We obtain the three dimensional sound impression and thus the directional information by means of adjustable phase differences between the stereo signal in the foreground and the Surround- Signal in the background