Leírások
Az optikai szál egy igen tiszta, néhány tíz (a technológia megjelenése idején még néhány száz) mikrométer átmérőjű üvegszálból és az ezt körülvevő, kisebb optikai törésmutatójú héjból álló vezeték. Működési elve a fénysugár teljes visszaverődésén alapul: A fénykábel egyik végén belépő fényimpulzus a vezeték teljes hosszán teljes visszaverődést szenved, így a vezeték hajlítása esetén is – minimális energiaveszteséggel – a szál másik végén fog kilépni.
CHART 1: COAX, UTP, AND FIBER COMPARISON
Cable diameter(inch), CableWight(lb/1000'), Attenuation@5MHz (dB/100') ShieldingEffectiveness (dB) Rated Distances (feet)
Mini Coax .146 16.0 1.3 80 350
RG59 Coax .242 35.0 .58 80 750
RG6 Coax .272 42.0 .47 80 1500
Cat 5e UTP (passive) .200 20.9 1.22 40 1000
Cat 5e UTP (active) .200 20.9 1.22 40 3000
Fiber (multimode) .13x.23 13.5 <0.5 N/A 6500
| Coaxial cable has been the standard of video transmission for years. It consists of a conductor (usually bare copper) surrounded by a polyethylene dielectric. Coax is shielded with a metal braid and/or foil to protect against electromagnetic interference (EMI). Coax is a popular and proven technology. Because almost all CCTV cameras and monitors accept coax connections, no media conversion is required. Coax's low attenuation and resistance to EMI makes it an excellent choice for transmission distances of as long as 1500 feet (and longer if repeaters are u sed) | Both inbound video and outbound PTZ (Pan, Tilt, Zoom) commands can travel over the same cable. Unshielded twisted pair (UTP) is a newcomer to the CCTV industry although it is the cable of choice for structured wiring data networks. A pair of insulated copper wires is twisted together to form a balanced transmission line. The balanced pair offers some protection against EMI (though typically not as much as a coaxial cable). UTP requires media conversion (baluns) to modify 75ø video RF signals for transport over 100ø UTP. Not all baluns permit PTZ commands to travel to the camera. However, UTP offers reasonable performance up to 1000 feet and longer if the baluns are powered (active). UTP cable is finding a role as the cable of choice for integrated security systems, where video, alarm monitoring, access control and asset tracking are all carried over a single network. UTP's small diameter, light weight, low cos |
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Coaxial cable has been the standard of video transmission for years. It consists of a conductor (usually bare copper) surrounded by a polyethylene dielectric. Coax is shielded with a metal braid and/or foil to protect against electromagnetic interference (EMI). Coax is a popular and proven technology. Because almost all CCTV cameras and monitors accept coax connections, no media conversion is required. Coax's low attenuation and resistance to EMI makes it an excellent choice for transmission distances of as long as 1500 feet (and longer if repeaters are u sed)
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