Musical doorbell (CB9210E)

This musical doorbell was found in a Popular Electronics from the 90s. The U4 melody generator integrated circuit is uncommon today.

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Modern Crystal Radio I (CB932E)
This modern XTAL radio replaces the galena crystal for a germanium diode as the 1N34 or...
Loudness Control (CB19814E)
This passive loudness control was obtained in an old publication. The critical component is the...
Analog Multiplexer (CB21250E)
This low impedance circuit was found in an Electronic Design from the 90's. Operational amplifiers admit...