Found in American documentation from the 90s, this circuit has the signal frequency determined by capacitors from C4, C3, C2 and C5 selected by digital switches.
The circuit shown in the figure is triggered by an input voltage determined by the setting of P1....
This circuit was found in Motorola documentation from 1969. The transistors are from that time. The...
This VCA was found in the July 1988 issue of Radio Electronics magazine. It uses an OTA op amp and...