This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even adapted to act as a shield. The circuit has the frequency given by C1 and adjusted in R1.
This basic 100 kHz oscillator is suitable for use in calibration. We found it in documentation from the...
Found in a 1968 EEE, this circuit accepts frequencies from 1 to 1000 Hz and control voltages from 0.1 to...
National Semiconductor suggests the circuit shown in the figure for amplifying signals from two...