Chapter 1. Introduction
61200063L1-20
DSU III TDM User Manual
1-5
Entering Dial Backup Mode
When a condition for entering dial backup mode is detected, the
Alarm
led
turns on, and the buzzer sounds. The buzzer alternates between 30 sec-
onds on and 30 seconds off unless the DDS line is restored or it is disabled
by using the
Quick
key and selecting
T
URN
O
FF
B
EEP
. See the section Front
Panel on page 3-10 for more information on the
Quick
key.
The following conditions can be enabled to cause the DSU III TDM to enter
dial backup mode:
Loss of Sealing Current
Sealing current is a low voltage DC current provided by the central office
(CO) to prevent corrosion of splices in copper wires used in the local loop.
Sealing current may also be used for local loop testing purposes. An ab-
sence of sealing current generally is an indication that the loop is open.
Out of Service (OOS) Signal
An OOS signal, generated by the network, indicates a device (or devices)
in the network is out of service. If the network has an excessive rate of er-
rors, the DSU III TDMs can no longer communicate, causing an out of sync
condition and resulting in dial backup operation if this option is selected.
No Receive Signal
This is an indication that the local loop copper pairs may be either open or
shorted or the OCU in the telco central office is inoperative. In a private
network this may indicate that the transmitter of the remote DSU is inop-
erative.
All 1s or all 0s Condition
This condition is usually generated by the network to indicate some device
(or devices) on the network is inoperative. Upon detecting an all 1s or all
0s condition, the DSU III TDM will initiate a handshake routine to deter-
mine whether the remote unit's DTE is the source of the all 1s or 0s condi-
tion or an actual network failure exists.
For more information see the chapter Configuring Dial Options on page 9-1.
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Страница 12: ...xii DSU III TDM User Manual 61200063L1 20 Table of Contents Appendix F Glossary F 1 Index 1...
Страница 16: ...xvi DSU III TDM User Manual 61200063L1 20 List of Tables...
Страница 24: ...Chapter 1 Introduction 1 8 DSU III TDM User Manual 61200063L1 20...
Страница 44: ...Chapter 3 Operation 3 14 DSU III TDM User Manual 61200063L1 20...
Страница 72: ...Chapter 4 Testing and Troubleshooting 4 28 DSU III TDM User Manual 61200063L1 20...
Страница 86: ...Chapter 7 Configuring DTE Options 7 8 DSU III TDM User Manual 61200063L1 20...
Страница 90: ...Chapter 8 Configuring Test Options 8 4 DSU III TDM User Manual 61200063L1 20...
Страница 108: ...Appendix A Pinouts A 6 DSU III TDM User Manual 61200063L1 20...
Страница 112: ...Appendix B Configuration Profiles B 4 DSU III TDM User Manual 61200063L1 20...
Страница 114: ...Appendix C DSU to Modem Interconnect C 2 DSU III TDM User Manual 61200063L1 20...
Страница 116: ...Appendix D EIA 232 Connector D 2 DSU III TDM User Manual 61200063L1 20...
Страница 120: ...Appendix E Specifications Summary E 4 DSU III TDM User Manual 61200063L1 20...
Страница 130: ...Appendix F Glossary F 10 DSU III TDM User Manual 61200063L1 20...
Страница 136: ...Index 6 DSU III TDM User Manual 61200063L1 20 Index...