Shielded line

A shielded line comprising a central wire; a shielding conductor disposed around the central wire; and the central wire and shielding conductor being divided into first, second and third parts where (a) the central wires of the first and third parts are connected to the shielding conductor of the second part and (b) the central wire of the second part is connected to the shielding conductors of the first and third parts so that a signal applied to the central wire of the first part flows through the central wire of the first part, the shielding conductor of the second part and the central wire of the third part and a signal applied to the shielding conductor of the first part flows through the shielding conductor of the first part, the central wire of the second part and the shielding conductor of the third part.

BACKGROUND AND OBJECTS OF THE INVENTION 
This invention relates to an improvement of the signal transmission lines 
and, mainly, to single wire, shielded, coaxial lines. 
Single wire, shielded, coaxial lines have heretofore had plugs 1 at both 
ends as illustrated in FIG. 1. A braided, shielding conductor 3 around 
central wire 2 is provided with insulating material in between. The 
conductor 3 eliminates the mutual inductance and also prevents the 
electromagnetic coupling. Generally, a signal line (not shown) is 
connected to central wire 2 and the earth line (not shown) to the 
shielding conductor 3. Accordingly, the signal voltage of and current in 
shielding conductor 3 are constantly subjected to electrostatic influence 
by external electrostatic fields. Thus, for example, external AC fields 
modify the electric potential between two lines 2 and 3 and accordingly 
generate induced current. Hence, the transmitted signal is distorted with 
an attendant reduction in S/N ratio. 
It is thus an object of this invention to provide a shielded, coaxial line 
which lessens the aforesaid defects by reducing induced current and 
minimizing the electric potential difference between the signal line and 
the earth line. 
Other objects and advantages of this invention will be apparent from a 
reading of the following specification and claims taken with the drawing.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
Reference should be made to the drawing where like reference numerals refer 
to like parts. 
FIG. 2 is a wiring diagram of a distribution line of this invention 
illustrating the relationship between the central wire of a single wire, 
shielded line and the shielding conductor and with plugs 1 on both ends. 
The effective length L is divided into parts A, B, and C with A and C 
corresponding to the relationship of existing central wires and shielding 
conductor 3. Core part B reverses the signal route extending through the 
central line 2' and the shielding conductor 3'. Thus, at point D, 
shielding conductor 3 of part A is connected to central wire 2' of part B 
and central wire 2 of part A is connected to shielding conductor 3' of 
part B. Also at point E, the central wire 2' of part B is connected to 
shielding conductor 3 of part C and shielding conductor 3' of part B is 
connected to central wire 2 of part C. Accordingly, the input current from 
the signal line is transmitted via 2 of part A, 3' of part B, and 2 of 
part C while the input current from the earth line is transmitted via 3 of 
part A, 2' of part B, and 3 of part C. Also, the ratio of the effective 
length of the (A+C) parts to the effective length of part B should 
preferably be 1:1 where the position of part B need not be restricted to 
the central portion of the shielded line. Rather, part B may be randomly 
positioned although the phase of the input signal to part A should be 
equal to that of the output signal from part C. That is, there should be 
three or an odd number of parts to restore at the output the original 
phase relation at the input. 
FIG. 3 is a wiring diagram of a modified, distribution line in accordance 
with the invention where the signal current of the earth line flows 
through the shielding conductor at the parts A and C corresponding to A 
and C of FIG. 2. Since the signal current of the signal line flows through 
the shielding conductor at part B, an equal amount of electrostatic 
influence and magnetic influence occur due to external electrostatic 
fields. Thus, an external AC field goes through both the signal line and 
the earth line and make it possible to reduce the relative potential 
difference between the lines and the induced current. Also, despite the 
slight difference of the pure resistance value with the central wire and 
the shielding conductor of conventional, coaxial lines, it can be 
recognized that the resistance value of the signal and earth lines is 
exactly the same in the present invention. 
A shielded line (FIG. 4) having a double shielding function may also be 
implemented by providing a conductive shield 4 around over the shielding 
line of FIG. 2 and connecting shield 4 to plug 5 on one end of the ground. 
In one working implementation (FIG. 5) of the FIG. 4 embodiment, an audio 
phono-cord is provided. Each central wire is connected to one of the 
shielding conductors at a position 1/4 (D' part) and 3/4 (E' part) of the 
effective length from the plug 5. Of course, the shielding conductors are 
also connected to the central wires at these points to one of the core 
lines. No distortion occurs so that a balanced regenerated tone quantity 
results with a good rise from low to high level hearing sensitivity. 
In another working implementation of the invention, an improved effect 
equal to the regenerative tone quantity obtained with the above-mentioned 
working implementation was also produced for an audio speaker cord with 
the shielded line structure of this invention. 
Although the embodiments and implementations of this invention have been 
described for audio, the shielded line of this invention is not limited to 
single wire, shielded, coaxial lines and other shielded lines in 
accordance with the invention may be used for telecommunication or 
measuring devices or other transmission systems. Further, the shielded 
line described hereinbefore may be replaced with other lines such as 
parallel lines, twisted pair lines, etc. 
Thus, this invention lessens the distortion and the reduction in S/N ratio 
caused by external field induction. 
It is to be understood that the above detailed description of the various 
embodiments of the invention is provided by way of example only. Various 
details of design and construction may be modified without departing from 
the true spirit and scope of the invention as set forth in the appended 
claims.