Specifications

Operating Modes
2-7
Two user-selectable modes of operation are available:
• V.32bis - compliant with CCITT recommendations. This mode does not support
a secondary channel. Therefore, if the unit is a remote and a CMS link exists
during normal operation (all operating modes except CC64), the link is lost when
the unit is in dial backup operation.
• V.32bis+ - an enhanced Milgo mode which supports a secondary channel.
Secondary channel data is transmitted using a constellation multiplexed scheme.
This channel is compatible with the Milgo T7 channel. Therefore remote units
that did not have a continuously available CMS link (DDS operating mode)
during normal operation will have this link when the unit is in dial backup
operation. For remote units, the DAP provides an NMI connector for Second
Level T7 devices. This mode is not compliant with CCITT recommendations
and should only be used when connecting to another Excalibur DAP with Analog
IDBU.
The following features are not available when the DAP is in dial backup operation:
• Clear Secondary Channel
• Rate Adaption
When configured for automatic dialing, the DAP places the required telephone call in
response to one of the following user-selectable conditions:
• DDS Down - DDS goes down due to Out of Service codes, Abnormal Station
codes, loss of multiport framing, or loss of network framing for a user-selectable
time period.
• No Signal - an invalid DDS signal is received from the network.
• Network Down - the DAP dials after the DDS network goes down or an invalid
signal is received from the network.
• DTR - the DAP dials when the DTR signal is active. This setting allows external
routers and FRADs to originate dial backup calls.
Note: The DAP will not automatically dial when it is in a test state such as End-to-End
Network Loops.
You may select any DAP in the network (remote or central) for automatic dialing. Both
DAPs can answer a call, but only one should be configured to automatically originate the
call.
When a dial backup connection is initiated (through any of the methods), the following
events occur:
1. The originating DAP goes off-hook and dials the previously stored primary
telephone number of the answering DAP.