9 V to 5 V converter LT1175 (CB14616E)

We found this circuit in the 1997 Linear Technology Applications. The components used were common at the time.

Sinusoidal to square converter (CB9614E)
This shield circuit uses a common CMOS port. The voltage depends on the interfaced logic. The...
Audio Frequency Counter (CB21054E)
This circuit was published in Popular Electronics from the 90's. The components are common, as...
Low voltage motor control (CB22121E)
This circuit with SCR was found in an old documentation. The SCR can be the TIC106, and the...