Adsl Splitters - HP ProCurve Secure 7000dl Series Basic Management And Configuration Manual

Customers who have ISDN equipment such as telephones and fax machines
can continue using this equipment while moving their Internet or WAN con-
nection to ADSL. Support for ISDN is called ADSL over ISDN, or ADSL Annex
B, and is common in countries such as Germany where ISDN is popular.
.14 MHz
0
POTS
ISDN
Upstream
Figure 7-5. ADSL with POTS or ADSL with ISDN

ADSL Splitters

Because ADSL supports analog voice or ISDN traffic, the local loop is a shared
medium. In an ADSL Annex A environment, telephones send analog voice over
the local loop, and the WAN router sends digital data. At the CO, the analog
voice must be transmitted to the voice switch and then routed over the public
carrier network. The digital data, on the other hand, must be transmitted to
the DSLAM and then routed over the regional broadband network. At the
customer's premises, the analog voice must be sent to the telephones, and the
digital data must be sent to the WAN router.
To separate the analog voice from the ADSL data, a POTS splitter is installed
at both the customer's premises and the public carrier's CO. The POTS splitter
filters the traffic at both ends of the local loop and ensures that the analog
voice and the ADSL traffic are sent to the appropriate device at each location.
In an ADSL Annex B environment, ISDN equipment and the WAN router
transmit data over the local loop. At the CO, the ISDN traffic must be trans-
mitted to the ISDN switch and then routed over the public carrier network.
The ADSL data must be transmitted to the DSLAM and then routed over the
regional broadband network. At the customer's premises, the ISDN data must
be sent to the ISDN equipment, and the ADSL data must be sent to the
WAN router.
Downstream
Upstream
Downstream
ADSL WAN Connections
ADSL Overview
2.2 MHz
ADSL with POTS
ADSL with ISDN
7-9