Found in a 1980s American documentation, this circuit operates with 5 V signals requiring 55 cycles of 500 Hz for tone recognition. The circuit can be adapted to operate with other frequencies.
Found on Popular Electronics from the 1990s, this oscillator uses a general purpose transistor. The...
This circuit was obtained from National Semiconductor documentation from the 1990s. The circuit has a...
We found this circuit in a 2005 Linear Technology manual. Observe the component values and...