Hi Robbie,  Thanks for the explanation regarding the Dynavoice roll
motor speed control.  I thought the following might be of interest
to some MMDers.

In my original posting I described the uninterrupted wire going to
the motor coil as the "Grounded Conductor", which was changed in the
posting to "neutral" (commonly thought of as the "white wire").

"Grounded Conductor" is the correct term, as the "white wire" or more
correctly the "identified wire"; it is not always a "neutral".

In a 2-wire system the "Grounded Conductor" is not referred to as a
"neutral".  The term "neutral" may be correctly applied in a 3-wire
system, e.g., a typical 3-wire 220/240-volt residential system.  It
refers to the conductor from the center tap between the two 120-volt
legs of a power transformer and is the "Grounded Conductor" of that
system.

I realize there are more complicated hook-ups, like 3-phase, etc., but
to keep it simple, let's assume a simple 120/240-volt transformer with
a center tap, that's hanging on a pole outside your residence.

I know this can be a little confusing,  because there is also the
"Grounding Conductor", or more commonly, the "Ground Wire".

The "Grounding Conductor" carries transient voltage to ground if there
is a ground-fault, a short, etc.  It should not be used to carry
operating current.  (But I have seen it!)

The "Grounded Conductor" correctly refers to the grounded current
carrying conductor of a 2-wire system or to the "neutral" of a 3-wire
system, (or 5-wire system, etc.).

"Identified Wire" or "Identified Conductor"  refers to the Grounded
Conductor in a given system.  If your electrical system is properly
color coded throughout*, this would be the white wires of the system.

Look closely at common zip cord on small appliances and lamps and you
notice that one side of the cord has a ridge or is grooved on one side
of the cord.  This is the "identified conductor" and should be
connected to the larger prong of a polarized plug.  The larger prong
plugs into the "Grounded Conductor" of the plug receptacle, thus
ensuring that the "hot" side of the cord goes directly to the switch.

This, of course, is just that much safer than many older appliances
using non-polarized plugs, were you have a 50/50 chance that the whole
appliance is hot and just looking for a ground to complete the circuit.

Of course, the next level of safety is afforded if you have a 3-prong
plug/cord system, which also will "Ground" the cabinet, of an appliance.

There is a commonality between the "Grounded Conductor", and the
"Grounding Conductor" as they are required to be connected to each
other at the service panel, also to the service panel cabinet, and
thence to a "Ground Rod", also the nearest "uninterrupted" water-filled
cold water line of a residence or business for maximum safety of the
electrical system.

In the interests of safety, some localities require that the gas lines
and hot and cold water systems all be connected to the same ground to
eliminate any potential electrical differences between them.

* A problem may arise when "Romex" type cable is used in switch legs
and is not properly identified.  The result is white "hot" wires: white
wires being directly connected to black wires, etc.  Proper installation
in this case calls for painting or black taping or otherwise altering
the white wires where they are exposed so that they are seen as black.

Tom Lear
San Francisco, CA

 [ The term is confusing because "ground" can be either the green
 [ "ground wire" or it can mean "ground potential".  Since you didn't
 [ mention safety ground I assumed you spoke of the "neutral" wire
 [ which carries the return current of the motor.
 [
 [ I believe that the U.S. electrical wiring recommendation reserves the
 [ term "ground" or "safety ground" to signify the earth connection via
 [ a water pipe or similar; normally no current flows through this wire.
 [ In single-phase wiring "neutral" is the conductor which carries the
 [ return current; it is at approximately earth potential.  The standard
 [ colors in USA are green for safety ground, white for neutral, and
 [ black for the "hot" wire.  -- Robbie