This circuit was found in an Electronics World of 1968. Its purpose in triggering a relay when the circuit receives signals from a vibration sensor. The circuit is used in emergency situations.
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals...