As part of the spring maintenance of the Seabreeze carousel organ,
I adapted a leaf from Ross Davis's book and hooked up the nickel trip
hole in the tracker bar to a couple of LED displays (using the hour
division from two digital clocks), so that the public can now see,
by looking at the tune lists on the two rolls being played each day,
exactly what tune on what roll is currently playing. Fortunately no
roll has more than 12 tunes on it, since the clock hour section goes
only from 1 to 12.
Ross used to have an easel with 10 light bulbs set up at the Griffith
Park M-G-R with the light bulbs sequenced by the nickel trip hole in
his rolls. On the easel he'd place a large tune card for the rolls
playing, titles lined up with light bulbs, the lit one indicating the
playing tune. I'm told that apparatus is still up in the attic of the
Griffith Park M-G-R.
The LED system is much more compact, safe, and energy efficient. The
nickel-trip unit block triggers a tiny internal microswitch to control
the LED's numeral advance and a larger DPDT microswitch operated by the
slide valve that sends the vacuum supply to one side or the other of
the transfer chest controls which of the two LED displays (each mounted
under its respective roll box label) is lit.
Maybe my description is confusing, but the thing works, and people who
are interested can know the name of each tune they are hearing at the
Seabreeze merry-go-round. We have a complete set of over 130 Wurlitzer
165 rolls, and unfortunately as time goes on fewer and fewer people
recognize fewer and fewer of the tunes.