It is small and nice device made in the style of Panasonic.
This converter that allows you to receive TV sound on a simple FM receiver tuned to the frequency of 108.3 MHz.
On the side there is a spring-loaded bracket that allows you to fix the device on the whip antenna of the FM radio. The only condition - the device must have a direct connection to the telescopic antenna.
If the antenna is insulated on the outside, the device will not work directly. In this case it is necessary to connect a separate antenna to the top screws and, with a single wire, connect device output to the antenna input (or directly to antenna) of the FM radio.
Below you will find original Operating Instructions from Panasonic on how these connections must be made. Several other documents, which were included in the package, are very interesting to read, too.
In any case, we have a converter that converts TV audio carrier frequencies for channels 2 - 6 and Ch.7 - Ch.13 to the 108.3 MHz, at which your radio must be tuned.
On the wiki, you can find tables that show the frequencies assigned to broadcast television channels in various regions of the world. To be more precise, they were attached to each analog television channel in different countries. Right now it does not matter, because all jumped on the digital television, the majority (or all) of these channels are free of analog TV.
OK. Here are a few photos of how it looks like.
Right now is the time to see what is inside.
The following two pictures show the same thing, only more detailed.
On the right photo you can see two contacts, made of conductive rubber, which are connect converter to the antenna.
I did not take schematic diagram from this device, but an educated guessing shows that this is a well done VHF converter.
On one side - receiver, which covers frequencies 59 to 88 MHz and 179 to 216 MHz.
On the other side - FM transmitter operating at 108.3 MHz.
In the middle - a ceramic 'band pass' filter.
No matter how well it was done, it's dead to receive the TV sound. Just because there is nothing to take. Analog television is no longer in air.
But it does not make this device useless. Why? Because it is the best and simple tool that allows you to find bugs (small transmitters with a microphone). In order to determine whether the wireless microphone in the room does not take more then one minute. And it much faster than scan the place with any special equipment.
And, of course, it can be used as a receiver for the same FM radio microphones, operating in the frequency range 59 - 108 MHz, or 179 - 216 MHz (range 88 - 108 MHz FM radio covers itself). If FM transmitter is far away, you can connect an external TV antenna, according to the labels on the back side of converter housing.
Next to the photo of the packaging box, you can find a scan of the documents (*.pdf) that were in.
5. Panasonic RD-9580. Nearest Authorized Servicenter. Page 1
P.S. It is interesting that even after 40 years, this device is still alive.