This circuit was found in Texas Instruments documentation from 1968. The transistors are from that time, admitting modern equivalents. The response ranges is from 20 to 20 000 Hz.
This source circuit, published in 1988, incorporates a timer with integrated circuit 555. In this...
This beacon causes an LED to flash with the mains voltage. The frequency depends on the capacitor. For...
Found in a 1970 EEE, this circuit uses general-purpose transistors of the time. Transistors support...