[dagskarlsen]

Here are some used in Norway:
The banana was used in the 70ies, later came the blue and orange ones. The las tone was made in Oslo-telefonanlegg (O.T.A.) by the workers there from the beginning, and until the banana was introduced.

dsk

Edit
Uploaded 2 more pictures, the diagram is from the Banana No induction coil, just resistors. It was working better with just transmitter and receiver in series!