T+A POWER BAR 2+3 Operating Instructions Manual page 10

Radiated interference
Mains-borne
interference
Interference can affect a Hi-Fi system by several different routes,
and suitable measures need to be taken to avoid each potential
problem.
In the modern world we are constantly surrounded by high-
frequency electro-magnetic interference fields. The mains leads
and inter-connects of a typical Hi-Fi system can act as aerials,
picking up these fields and passing them on to the devices to
which they are connected. The POWER BAR mains panel and
POWER LINE mains leads are completely shielded all round,
and the shield prevents stray electrical fields reaching the internal
conductors; instead they are simply passed to earth. The
construction of the conductors in  mains leads is arranged in
such a way that open conductor loops cannot arise, and this
means that magnetic fields cannot occur within them.
The wires of the mains power supply network also tend to act as
aerials. A further problem is that the mains supply is usually
connected to a wide range of equipment which generates
powerful interference, such as computers, switching units, control
systems and motors, all of which inject a broad spectrum of
interference into the mains supply. This interference is passed on
via the mains network and inevitably reaches the sensitive Hi-Fi
equipment - unless prevented. All  Hi-Fi components feature
internal mains filters which guard against this type of incoming
interference, but it is always better to suppress the interference
before it reaches the equipment rather than provide protection
inside the unit itself. The POWER BAR provides effective
protection in the form of symmetrical PI filters with current-
compensated inductivity, and these filters absorb a broad band of
mains-borne interference and prevent it reaching the system. The
filters are complemented by ferrite rings which are fitted to the
outer sleeves of the POWER BAR supply cable and POWER
LINE mains leads. The ferrite rings suppress interference fields,
prevent them penetrating into the system, and also prevent them
passing from device to device.
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