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.
The figure shows how to obtain a locking relay for an alarm circuit with sensors in series and in...
Found in Popular Electronics from 1969, this circuit uses a neon lamp from the time that had...
This is a simple rheostat circuit for motor control that works with voltages from 6 to 12 V. The...