With this simple circuit it is possible to simulate a telephone line for carrying out repairs on telephone sets. The transformer must be 36 V and the diode can also be 1N4004.
With this circuit from Popular Electronics it is possible to determine the characteristics of a microammeter...
This circuit can be implemented with other operational ones. We found it in documentation from the...
I found this circuit in a 1979 documentation. The phone must be at least 1k magnetic or crystal...