ADTRAN ISU 128 - Manual (Page 69)

Chapter 7. Protocol Options
54 ISU 128 User Manual 61202.029L2-1
FALLBACK
The FALLBACK asynchronous rate adaption protocol provides the capability
to automatically establish calls with other ISDN terminal adapters, Switched
56 DSUs, V.34 modems (optional), as well as other ISUs using a single config-
uration. To communicate with analog modems, the ISU 128 with V.34 modem
option (part numbers 1202029L3) must be used.
The ISU 128 must be optioned as follows for FALLBACK operation:
• Any asynchronous bit rate up to 115.2 kbps which is supported by the
DTE.
• Flow control must be enabled and supported by the DTE.
FALLBACK supports the following protocols based on the call type: BOND-
ING Mode 1, V.120, T-Link, and V.34.
When answering calls, the ISU 128 uses the incoming call type to determine
which rate adaption protocols to support. See Table 7-A for the call type and
the supported rate adaption protocols.
Table 7-A
Rate Adaption Protocols
Call Type
Rate Adaption
Protocols Supported
Typical Units Supported
Data 64k BONDING Mode 1 ISUs
V.120 ISDN TAs
PPP PPP compatible bridges/routers
Data 56k V.120 ISDN TAs
T-Link 2-Wire Switched-56 DSUs
PPP PPP compatible bridges/routers
Speech or Audio V.34 V.34 compatible modems