Page 13 of 130
Figure 6: Single Line with POTS and DSL connection
Resistance
The degree to which a conductor or an electrical circuit opposes an electrical current flowing through
it. It is somewhat analogous to the idea of friction, which in mechanical systems opposes the
movement of equipment. In electrical circuits, resistance is measured in Ohms. Ohms law serves to
describe the relationship between resistance, voltage and current in an electrical circuit.
Ohms law states that Resistance = Voltage / Current (R=V/I).
We typically speak of resistance in DC circuits whereas in AC circuits the term impedance is used.
While all cable has a characteristic amount of resistance built into it, which resistance is taken into
account, when a circuit is designed, and it does not adversely affect the function of the circuit.
Typically speaking, the shorter the cable, the less resistance.
For example, you wouldn’t hook up your CD player to your speaker with 1000 meters of speaker
wire. You would use the shortest wire possible.
Less Resistance = Less Attenuation = Better Signal
However, there are many things that can cause the resistance to either increase or decrease, thus
causing problems. Items and situations to be aware of include:
Connections to equipment and within equipment (i.e. hang up-switch) may become loose, dirty, wet,
broken, old (corroded). In fact, anything less than an ideal connection can increase or, in the case of
a short, decrease the resistance.
Using the CD player analogy again, you wouldn’t connect your player to your speaker with ten
chunks of speaker wire or various gauges twisted together.
Fewer Connections = Less Resistance = Better Signal
Improper resistance can throw off the cable balance, increase susceptibility to noise, cause crackling,
static, grounds, shorts and other problems.
Frequency Response
The characteristic of a cable that will determine how closely the signal that is input to the cable will
resemble the signal that is output after having traveled along the cable. Ideally, each frequency
transmitted on the cable will be received with identical attenuation. However, the reality is that not
all frequencies arrive equally attenuated. The frequency response of the cable will tell you what the
attenuation for a set of frequencies will be.
Lower frequencies travel farther distances than higher frequencies because of their wavelengths, but
higher frequencies can hold more information.
Example: AM radio (typically lower fidelity, mono) vs FM radio (higher fidelity, stereo).
Capacitance
In electrical circuits, refers to the mutual capacitance between two conductors. The result of
capacitance is that each conduct can impact the other, electrically, causing degradation of the signal.
