ZyXEL Communications ACCESSING INTERNET & INTRANET omni series - Manual (Page 46)

34 ISDN Communication Basics
AT&L0 - Analog adapter 1 has the higher priority to answer a voice
or voice-band-analog-data call; if analog adapter 1 is busy, the call
will be routed to analog adapter 2.
AT&L1 - Analog adapter 2 has the higher priority to answer a voice
or voice-band-analog-data call; if analog adapter 2 is busy, the call
will be routed to analog adapter 1.
Multi auto-answering of data calls
When an ISDN data call comes in, the TA can determine the protocol
to be used in one of two ways:
1. By way of the information conveyed by the SETUP message (for
DSS1, these include the Bearer-Capability, Low-Layer-
Compatibility, or High-Layer-Compatibility information
elements; for 1TR6, these include the Service Indicator as well as
an Additional Octet of the Service Indicator)
2. By the Multi Auto-answering process. The TA determines the
protocol by monitoring the B channel signal sent by the calling
site.
With either method, the data call can be identified by the TA to be
X.75, V.110, V.120, or PPP, MPPP Async-to-Sync conversion.
If the address-matching process is again unable to tell which protocol
to use, the TA will go into its “Multi Auto-answering Routine,” by
examining the B channel data pattern and hence determine the
protocol to use.
When alerted, the TA will send a RING message to the DTE in the
following format:
RING
FM:17145522863 TO:17142630398