User Manual

VF / DSL Cable Qualifier

5.5 Industry Standard Test Loops

ADSL, HDSL, and ISDN modems are generally designed to operate on Industry Standard Test Loops. It is

quite possible to have a real local loop, which is shorter (distance) than one of the various test loops (see

Appendix A - Ideal Cable Results) and not have error free transmission.

This is usually caused by:

1. Bridge taps,

2. Load coils,

3. Uneven pair twisting

4. Bad splices,

5. Water in cable, etc.

Please note that ISDN U Interface devices are designed to work on the sixteen test loops as designated by

ANSI T1.601-1995. HDSL modems are designed to work on Customer Service Area (CSA) test loops and

ADSL modems are designed to work on ANSI T1.413 test loops (see Appendix A).

Also note that Rate adaptive Asymmetric Digital Subscriber Line (R-ADSL) operates at a lower speed when

confronted with a local loop which is longer than one of the standard test loops, has a bridge tap longer than

those of the standard test loops or cables which are impaired with noise or other anomalies.

ISDN, HDSL, and ADSL (plus all other types of DSL) will not connect on local loops which have load coils.

5.6 Bandwidth Requirements

The various DSL technologies need different bandwidths on the line to operate a full potential. The

CableSHARK will help identify if a particular DSL is supported.

• ISDN requires approximately 200 kHz of bandwidth in order to operate.

• HDSL requires approximately 400 kHz of bandwidth in order to operate.

• G.SHDSL requires approximately 1 MHz of bandwidth in order to operate.

• ADSL requires approximately 1.1 MHz of bandwidth in order to operate.

• ADSL2 requires approximately 1.1 MHz of bandwidth in order to operate.

• ADSL2+ requires approximately 2.2 MHz of bandwidth in order to operate.