We found this bridge circuit in Electronics Now magazine from September 1995. The instrument can be from 50 uA to 1 mA. The trimpot value depends on this instrument.
This is the project found in a 1981 publication, but it is still viable. It is a simple AM...
This commercial earphone receiver was manufactured in the 1960s in Japan. It was powered by a 9 V...
This circuit was found in a European publication from the 1980s. The transistors can be the BC548...