This circuit generates quadrature signals, that is, with a 90-degree phase difference. The circuit must be powered by a symmetrical source and the frequency depends on the capacitors.
The circuit in the figure is based on an LM101A; diodes can be replaced with equivalents. The...
This circuit, with magnetic sensor, uses an operational amplifier of the time. The circuit is from...
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...