This circuit from Motorola is from 1968, appearing elsewhere on this site. The transistors admit equivalent and the relay is of the sensitive type for low voltage, according to the power supply.
This car battery power supply was found in the June 1990 issue of Radio Electronics magazine....
This stereo meter-indicator was found in the August 1971 issue of Radio Electronics magazine. The...
This filter was found in Texas Instruments documentation from the 1980s. The circuit uses a common...