High Speed Transmission Equipment
Protection Circuitry
Longitudinal protection was not used at either the ADSL Transceiver Unit – Central Office
(ATU-C) interface or the ADSL Transceiver Unit – Remote (ATU-R) interface due to the
absence of earth ground connections. (Figure 3.8) In both instances, the P3500SC MC
SIDACtor device and the F1250T TeleLink fuse provide metallic protection. For ATUs not
isolated from earth ground, reference the HDSL protection topology.
F1250T
TIP
ADSL
chip set
P3500SC MC
RING
Figure 3.8 ADSL Protection
Component Selection
The P3500SC MC SIDACtor device and F1250T TeleLink fuse were chosen to protect the
ATUs because both components meet GR 1089 surge immunity requirements without the
use of additional series resistance. Although the P3100 series SIDACtor device may be
used to meet current ANSI specifications, Teccor recommends the P3500 series to avoid
interference with the 20 VP-P x DSL signal on a 150 V rms ringing signal superimposed on a
56.5 V battery.
HDSL Circuit Protection
HDSL (High-bit Digital Subscriber Line) is a digital line technology that uses a 1.544 Mbps
(T1 equivalent) transmission rate for distances up to 12,000 feet, eliminating the need for
repeaters. The signaling levels are a maximum of ±2.5 V while loop powering is typically
under 190 V. (Figure 3.9)
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© 2002 Teccor Electronics
SIDACtor Data Book and Design Guide
®
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