Wagner Lipnharski wrote:
> <snipped>
> Each module should has only 6 pins (Vcc, Gnd, GndRet, Clock, Data and
> DataReturn) at each side (to propagate the signal).  The GndRet at the
> left side connector is just a tied down, so it can tells the module at
> its left "I am here".  In the absence of this signal, the module
> automatically connects Data to DataReturn wires, using a transistor,
> gate logic, whatever is low cost. This is an auto-loop-back.

Resistor, would be my thought?  Should work well & cheaply, say 10k or
so, then the switching's done "auto-magically."  A pic output pin, or
74HC logic, can overcome a 10k resistor <G>  Fewest parts solution <G>

  Mark