This circuit was found in a 90s Popular Electronics. It is used for the acoustic transmitters of 40 kHz, as several found in this section. Transistors support current equivalents.
This circuit synthesizes the tick of a metronome with the speed controlled in RV1. The circuit is...
This circuit sensor is an NTC with a resistance of the order of 2k. The SCR can be from the TIC...
This circuit generates approximately 30 Hz signals from a 3.3 kHz clock. The circuit was found at...