This filter is from the Linear Applications Handbook of the National Semiconductor of 1994. However, it can be used with other operational and modified to operate with other frequencies.
Found in a Popular Electronics from the 90s, this circuit makes use of an unusual integrated...
If the battery is good, the LED flashes. This simple tester uses an LM3909 integrated circuit. We found...
Coupled to a bell, this year 2000 circuit provides an indication for attendance, if the person is...