This circuit was found in a 1993 Electronics Hobbyst Handbook. The circuit operates in the FM range. The coil has 4 turns of 24 or 26 wire in a coreless form 0.5 cm diameter.
This filter rejects 1 kHz signals, being suggested by the manufacturer of the operational...
The circuit presented was found in a Japanese magazine in 1973. The circuit uses transistors of...
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...