This circuit that emits siren sound can be used in a fire alarm. We found it in an old American documentation. The signal must be applied to a good audio amplifier.
This circuit was found in a 1980s documentation. Modern operational amplifiers can be used. The...
This differential amplifier, found in a 1964 Electronic Design, has a gain of 30. The setting can be...
The figure shows how to connect a relay to obtain the latch effect. The circuit is from an...