The L1 coil is formed by 4 turns of wire 20 in the form of 0.5 to 0.6 cm without core. The circuit is from an 80's documentation. The range reaches a few tens of meters.
This circuit was obtained from a 1967 General Electric documentation. The circuit makes use of...
This configuration uses the 4 gates of a 7401 integrated circuit. The capacitors determine the...
This filter can be used to eliminate hum in sound equipment. Operational amplifiers can be 741 and...