Audio and video cabling systems are generally build using four different types of cables: 75 ohm coaxial cables for video and RF and digital audio, shielded single wire cables (coaxial construction) for unbalanced analogue audio signals used in consumer audio systems, shielded twisted pair wiring for balanced analogue and digital audio signals used in professional audio systems, and thick insulated wire paiur for speaker wiring. Besides that some AV-system installations use unshielded twisted pair wiring for transporting some control signals between equipments. Those are the basic cable types used in audio/video systems wirings.
Normally video transmission is done using 75 ohm coaxial cables, but using suitable video signal converter video signals can be transported more or less well through unshielded twisted pair wiring. The secret to sending signals over UTP is to balance them well in order to limit both radiation and noise pick up. This kind of unshielded twisted pair wiring method is used in many CCTV applications nowadays to use existing in-house twisted pair wiring instead of installing new coaxial cable for the CCTV camera.
Ground loops are annoying thing which exist in many audio and video systems and cause humming noise to sound and disturb the picture usually with dark moving bars. Ground loops are often things that only after the system is installed it can be determined if a problem will exist. Ground loops are an after-the-fact type of problem in which the end-user blames the installer, the installer blames the manufacturer, and actually nobody is at fault. Fortunately ground loop problems can be corrected if can locate the source of the problem and you know what to do to solve that problem.
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