This circuit was found in Texas Instruments documentation from 1968. The transistors are from that time, admitting modern equivalents. The response ranges is from 20 to 20 000 Hz.
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...