The circuit of a low-pass/high-pass filter is shown in Fig 18.7. It consists of two RC networks connected in series with a buffer amplifier.
The adjustable frequency characteristics are shown in Fig. 18.8. The following frequency limits can be selected.
Lower frequency 40, 80, 160 and 270 Hz; upper frequency 11, 9, 4.5, 3.2 kHz.
Fig. 18.6 Sound source width (dimension) control circuit
Fig. 18.7 Low-pass/high-pass filter circuit