E)
This audio filter was found in the August 1993 issue of Radio Electronics magazine. It cuts low and high frequencies corresponding to rumble and scratch noises that occur on turntables.
This circuit generates noise pulses for audio equipment probes. The circuit is from a 90’s 303...
This modulated light transmitter was found in a 90s Popular Electronics. In place of the lamp with...
This circuit, found in a 1958 magazine, is for reference only, since the components are not easy...