Having recently discovered your fantastic web site, I thought that
your members may be able to answer a question I have.  I have in my
collection a Philips Pianella Model C with a 5-roll changer.  While
this is not so unusual, an attachment, which looks original, could be.

A shaft, extending from the right of the carrousel pivot, is fitted with
a cylindrical contact block which has a brass slip-ring and 5 contacts
equally spaced radially, but in differing axial planes.  This should
become clear when I say that 5 metal finger contacts, side by side,
are pressed against the cylinder, each in line with one contact.

A sixth contact bears on the slip-ring.  The slip-ring is connected
to all 5 contacts so that when a finger touches one of the contacts,
a circuit exists between the contact finger and the slip-ring finger.
The 5 fingers are connected to a terminal block at the back of the
instrument, together with a "common" terminal.

I was told by the person from whom I bought the instrument (Siegfried
Wendel of Ruedesheim), that it was a switch system which displayed
the title of the roll being played on an "egg box" type illuminated
indicator board mounted on the top of the instrument -- missing, of
course.

However, during the restauration of the upper action, I discovered that
it was not an indicating device but a remote, random roll selector.
There is an electro-pneumatic valve operated by the switch device which
collapses a pneumatic causing the revolver change mechanism to bypass
the thread cycle and continue to revolve until such time as it is
presented with a "common" from the switch block (the circuit presumably
coming from a wall mounted box(es)).  On receipt of the common, the
bellows relax and the threading process starts.

As a matter of interest, the power for this control system was taken
directly from the 200 vdc supply for the instrument!  No thoughts of
safety in those days.

As I have not heard or read of any such mechanism, am I right in saying
that it is a rare accessory?

Best regards

Brian Cuff
Manor cottage, Church Lane,
Burghfield, Reading, RG30 3TG, UK