Found in Popular Electronics from the 1980s, this circuit uses two operational amplifiers from that time. The circuit has frequency and symmetry adjustment.
This circuit is from a 1979 publication. The sensor consists of plates or screens that, when...
Found in an 80's documentation this circuit uses an integrated from the uncommon era today. Other...
This circuit was found in a Popular Electronics from the 90s. It uses a LASCR which is a photo-SCR...