ADEMCO 8132, Установка и настройка, Страница: 13 / 88

Section 3: Communications Setup
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the digital modem by filters, thus guaranteeing uninterrupted POTS/ISDN, even if ADSL
fails. The high-speed channel ranges from 1.5 to 6.1 Mbps, while duplex rates range from 16
to 832 kbps. Each channel can be sub-multiplexed to form multiple, lower rate channels,
depending on the system.
ADSL modems provide data rates consistent with North American and European digital
hierarchies and can be purchased with various speed ranges and capabilities. The minimum
configuration provides 1.5 or 2.0 Mbps downstream and a 16-kbps duplex channel; others
provide rates of 6.1 Mbps and 64 kbps duplex. Products with downstream rates up to 8 Mbps
and duplex rates up to 640 kbps are available today. ADSL modems will accommodate ATM
transport with variable rates and compensation for ATM overhead, as well as IP protocols.
Downstream data rates depend on a number of factors, including the length of the copper
line, its wire gauge, presence of bridged taps, and cross-coupled interference. Line
attenuation increases with line length and frequency, and decreases as wire diameter
increases.