This circuit was found in a Popular Electronics from the 90's. The CMOS integrated circuit used is not very common nowadays. The range depends on the infrared LEDs. R7 can be changed.
This effects circuit can be used with microphones or guitars. The circuit is from an American...
This circuit generates pulses whose frequency depends on C1. The circuit can be powered by...
I found this circuit in a 1998 publication, but as all components are common, it can be easily...