At
the right is a remote 'wallbox' for a Seeburg jukebox. These were found at
tables or booths in cafes and diners across America from the 1950's. This
unit is now in our family room in the basement and no longer controls the
playing of 45 rpm records but a selection of 'mp3' files on a computer.
We purchased this unit on eBay and were not expecting it to be in working condition. Upon arrival, I opened it up and found that everything appeared to be there and that the internals may even operate.
A little investigation on the web uncovered enough information for me to get a 25 VAC transformer from Radio Shack and connect it to the appropriate terminals. While most of the light bulbs were burned out, the change mechanism, selection buttons and the motor that sends the selection to the main jukebox all seemed to operate.
The selection is transmitted from the wallbox via a sequence of contact closures. Connecting an oscilloscope up to the signal line showed that pulses were being delivered. This signal line was then connected to one of the digital inputs on a Rabbit Semiconductor TCP/IP board.
I wrote a C program for the Rabbit board that time-stamped every transition in the pulse train then listed the times in ms between the transitions. The sequence of pulses was easy to determine. It consists of a start pulse followed by 1-20 pulses for the letter, a 200 ms delay then 1-10 pulses for the number. The width of the pulses was about 50ms with 30ms between them. The program was quickly modified to perform the additional translation directly to the letter and number selected. Additional code was put in the program to send the selection data to a server via TCP/IP. In this case, the server is an old 133Mhz PC running windows.
The PC is also running a Java program that listens for the requests on the specified TCP/IP socket and queues the request to the mp3 player thread. The player simply gets the next song in the queue and 'execs' a program to play the song.
All songs are kept in a single directory and have names that begin with the number and letter they are associated with.
The next picture shows the Rabbit board and the transformer for the wallbox. The only connections to this board are 12VDC, the signal line and the ethernet connection. These are mounted up on a joist in the 'unfinished' part of the basement.
Here's the server that listens for requests from the Rabbit board. This computer is networked into the others in the house so that the kids can load their songs for playing. This system sits under the stairs in the basement and connects to an amplifier in the next picture. The amplifier is connected to speakers in the room with the wallbox.
