Product specifications

COMMUNICATIONS
Sharp Electronics Corporation
Of all the effects of frequency on a cable, impedance is the hardest specification to
understand. That is because it is the sum-total effect of resistance, capacitance, and
inductance when a frequency or band of frequencies is applied to the cable. Since it
describes the "total opposition to current flow" caused by these three factors, it too is
measured in Ohms.
Fire Ratings
The National Fire Protection Agency (NFPA) is a voluntary non-profit organization that puts
out the National Electrical Code (NEC). This book sets suggested standards for safe
construction of buildings. These standards include flammability testing of wire and cable.
The NEC code is voluntary. This means that a state, county, or city may or may not adopt
the code. The majority of the states and communities subscribe to the NEC, but you can’t
know for sure unless you ask.
The NEC book lists many different cable ratings. Unrated cables are those which will
not be installed, and which will be visible when in operation such as microphone
cables. In the 1999 NEC, they now state that any cable installed must carry a rating.
If this is how your inspector interprets the new rules, then unrated cables cannot
even be installed in a conduit.
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