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.
With this circuit, signals in the range of 10 kHz to 150 kHz can be received at close to 4 MHz...
This limiting circuit with an operational amplifier has an adjustable cut-off point and can use...
Published by Philips in 1965 documentation, the sensor for this circuit is a common LDR. The...