Specifications

Excalibur Multirate DAP Installation and Operation
2-12
Manual call disconnection requires that you enter commands through the DAP's front
panel or the CMS system console. The DAP then switches transmission back to the
dedicated line.
ISDN Integral Dial Operation
The Excalibur DAP's ISDN IDBU feature enables both the primary and secondary
channels to transmit data across the dial-up telephone line when the dedicated line fails.
The DTE data rate can not be selected when the DAP is in dial backup operation. The
rate selected for normal operation is maintained during dial backup operation.
Synchronous DTEs support up to 64 Kbps without a secondary channel and up to 57.6
Kbps with a secondary channel.
When the DAP is in dial backup operation with another DAP equipped with ISDN IDBU,
a non-interruptive secondary channel is provided when the DTE rate is 57.6 Kbps or
below (all DDS services except CC64). This channel is compatible with the Milgo T7
channel. For remote units, the DAP provides an NMI connector for Second Level T7
devices except when the operating mode is DDS or CC64.
When the DAP is in dial backup operation with another DAP equipped with Switched 56
IDBU, a non-interruptive secondary channel is provided when the DTE rate is 52.8 Kbps
or below. This channel is compatible with the Milgo T7 channel. For remote units, the
DAP provides an NMI connector for Second Level T7 devices except when the operating
mode is DDS. When the DTE data rate is 56 Kbps or above, no secondary channel is
provided. 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.
The Clear Secondary Channel feature is provided during dial backup operation with the
following restrictions:
• The 600 and 1200 bps channel rates are not available.
• When the far-end unit is equipped with Switched 56 IDBU, this feature is not
available if the DTE rate is 56 Kbps or above.
• This feature is not available when the unit is configured to support T7 diagnostic
traffic over the secondary channel.
Call Initiation
To establish the dial-up connection, the originating DAP must place a telephone call to
the answering DAP. The call can be initiated in three ways: 1) automatically by the
DAP, 2) manually through the DAP's front panel, or 3) manually through the CMS
system console. When configured for automatic dialing, the DAP places the required
telephone call in response to one of the following user-selectable conditions: