I ended that post with a conversation about positive
voltages having less than positive effect on curcuits.
Like 6 volts positive--5.999 positive also being a negitive
voltage to 6 volts,giving you a pos having less than positive
effect which may happen in some bias curcuits where a
signal voltage will affect bias.I wanted a broader look at this
on electronic chat. Maybe this can be explain better by a
member with a lot of experience with bias where you have
this effect of a pos being less than pos--being negitive.

 

here is an extremely old-school technique that was used to conserve conductor count in a wire harness.

note attachment 1:
2 12 volt batteries in series provides 24 volts.
However in this situation, a tap is pulled off from between the two batteries. This be the BLACK wire which is connected to two valve coils.

From the vantage point of this connection between the two batteries, looking up to the positive side would leave the BLACK wire being 12 volts less than the positive side of this 24 volt battery array (-12volts) and 12 volts more than the negative side of this 24 volt battery array (+12 volts).

Looking at the three position switch, if the switch is pushed counterclockwise, the BLUE wire at common will be connected to the RED wire from the Positive side of the 24 volt battery array.
Foregoing the conventional/electron flow argument, the Positive of the battery is being attracted by the 12 volt less Positive force on the valve coil through the diode on the right side of the valve. The valve spool would then move in a corresponding direction.

Likewise, if the three position switch is pushed in the clockwise position, the BLUE wire at common will be connected to the BROWN wire from the Negative side of the 24 volt battery array.
Again foregoing the conventional/electron flow argument, The Negative of the battery array is being attracted by the 12 volt more Positive (less Negative) force on the valve coil through the diode on the left side of the valve. The valve spool will then move in the corresponding direction.


12 volts being used on a valve coil is very inefficient. 24 volts is more commonly used. Current draw and affect on mass being a couple of reasons.
Attachment 2 shows the same concept except the 12 volt Valve Coils are replaced with 24 volt Valve Coils. 12 volt Relay Coils are in the circuit where the 12 volt Valve Coils were. The same action is taking place with the Relay Coils as was happening with the Valve Coils in attachment 1.
This time, the contacts of the Relay are providing 24 volts to the Valve Coils. Sit back and take the senic route through the drawing.

Attachment 3 is showing the reason for the method of wiring. Three valves can be controlled with a five conductor cable.
Remember, I said this was old school, very old school. No processors here!

This is an old biasing concept that works well and is tried and true.
Still being used here and there.

 

Loosewire,

probably one of the best examples of that is using opamps on a single supply with a local bias voltage produced by a resistive divider.

eg. on a 12V supply, the bias may be at 6V, with the supply split by two resistors.

From an outside view, all voltages are between 0 and +12, but taken from the opamp's bias point it can be seen as +6V & -6V

Everything is relative!

 

a biased voltage divider of sorts

 

Thanks guys,It shows the expertise that we have on the forum.
The new school has arrived,with there favorite avartars.