This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
This circuit was obtained from a Poptronics in June 2001. The magazine no longer exists, but the...
We find this circuit in a 1980s documentation. The circuit uses uncommon components today which can...
This circuit has a very high input impedance and a very low output impedance. We found it on a...