--- On Fri, 3/12/10, Steven C. Barr <[log in to unmask]> wrote:

> Metal
> (IIRC) portions at either end of the cartridge signaled the
> player to play
> the next set of tracks...this would continue (as I
> discovered one drunken
> night...?!) for as long as the player was operative...?!

It was sensing foil (the same concept as conducting tape used
by film chains in TV stations to switch between A and B
rolls of film).  The foil simply completed a circuit, which
activated a solenoid which rotated a ratchet 1/4 turn.
Connected to the ratchet was a 4-step cam that moved the
up and down.

"?!?!"