This circuit was found in a publication by Edelman from 1924. The power comes from the battery and the listening is through a high-impedance headphone.
This power supply with transistor regulation was obtained in a 1995 documentation. The power...
This two-station intercom was found in documentation from 1966. R4 should be experimentally...
We found this circuit in a publication from 1966. The components are from the period. Complete...