For an unamplified telephone line a twisted pair cable could only manage a maximum distance of 30 km.
Balanced line cable length.
A balanced electrical signal runs along three wires.
Any noise picked up along the cable run will typically be common to both legs.
A balanced cable by contrast has three conductors in the connector and three wires in the cable.
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However this did not become widespread until repeater amplifiers became available.
The cable construction used for balanced telephone cables was twisted pair.
With balanced cables you don t get the same distortions so they can be much longer without any detriment to your sound quality.
4 that said you would be nuts to try to run unbalanced for more than 25 feet or 50 at the most.
A ground a positive leg and a negative leg.
High levels speaker cable are rarely balanced.
Both legs carry the same signal but in opposite polarity to each other.
Open wires on the other hand with their lower capacitance had been used for.
As in the unbalanced cable the ground wire still surrounds the signal wires and is used as a shield against interference.
But what makes a balanced cable special is the way the gear utilizes that.
As a general rule this effect is only noticeable with cables beyond 20 feet in length.
That said when the cord length is under 10 feet unbalanced cables actually have a stronger signal than balanced cables.