This circuit was found in American documentation from the 1960s. The operational amplifier is from that time, but the configuration applies to modern equivalents.
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...
This circuit, which uses components still common today, was found in a 1997 documentation. It...
This circuit is intended to apply the music signal from a stereo to a telephone line for the...